economic and psychological dependency

chapter outline


·   Biological Aging Is Under Way in Early Adulthood

·   Aging at the Level of DNA and Body Cells

·   Aging at the Level of Tissues and Organs

· ■  BIOLOGY AND ENVIRONMENT  Telomere Length: A Marker of the Impact of Life Circumstances on Biological Aging

·   Physical Changes

·   Cardiovascular and Respiratory Systems

·   Motor Performance

·   Immune System

·   Reproductive Capacity

·   Health and Fitness

·   Nutrition

·   Exercise

·   Substance Abuse

·   Sexuality

·   Psychological Stress

· ■  SOCIAL ISSUES: HEALTH  The Obesity Epidemic: How Americans Became the Heaviest People in the World


·   Changes in the Structure of Thought

·   Perry’s Theory: Epistemic Cognition

·   Labouvie-Vief’s Theory: Pragmatic Thought and Cognitive-Affective Complexity

·   Expertise and Creativity

·   The College Experience

·   Psychological Impact of Attending College

·   Dropping Out

·   Vocational Choice

·   Selecting a Vocation

·   Factors Influencing Vocational Choice

·   Vocational Preparation of Non-College-Bound Young Adults

· ■  SOCIAL ISSUES: EDUCATION  Masculinity at Work: Men Who Choose Nontraditional Careers


The back seat and trunk piled high with belongings, 23-year-old Sharese hugged her mother and brother goodbye, jumped in the car, and headed toward the interstate with a sense of newfound freedom mixed with apprehension. Three months earlier, the family had watched proudly as Sharese received her bachelor’s degree in chemistry from a small university 40 miles from her home. Her college years had been a time of gradual release from economic and psychological dependency on her family. She returned home periodically on weekends and lived there during the summer months. Her mother supplemented Sharese’s loans with a monthly allowance. But this day marked a turning point. She was moving to her own apartment in a city 800 miles away, with plans to work on a master’s degree. With a teaching assistantship and a student loan, Sharese felt more “on her own” than at any previous time in her life.

During her college years, Sharese made lifestyle changes and settled on a vocational direction. Over-weight throughout high school, she lost 20 pounds in her sophomore year, revised her diet, and began an exercise regimen by joining the university’s Ultimate Frisbee team, eventually becoming its captain. A summer spent as a counselor at a camp for chronically ill children helped convince Sharese to apply her background in science to a career in public health.

Still, two weeks before she was to leave, Sharese confided in her mother that she had doubts about her decision. “Sharese,”her mother advised, “we never know if our life choices are going to suit us just right, and most times they aren’t perfect. It’s what we make of them—how we view and mold them—that turns them into successes.”So Sharese embarked on her journey and found herself face-to-face with a multitude of exciting challenges and opportunities.

In this chapter, we take up the physical and cognitive sides of early adulthood, which extends from about age 18 to 40. As noted in  Chapter 1 , the adult years are difficult to divide into discrete periods because the timing of important milestones varies greatly among individuals—much more so than in childhood and adolescence. But for most people, early adulthood involves a common set of tasks: leaving home, completing education, beginning full-time work, attaining economic independence, establishing a long-term sexually and emotionally intimate relationship, and starting a family. These are energetic decades filled with momentous decisions that, more than any other time of life, offer the potential for living to the fullest.



We have seen that throughout childhood and adolescence, the body grows larger and stronger, coordination improves, and sensory systems gather information more effectively. Once body structures reach maximum capacity and efficiency,  biological aging,  or  senescence,  begins—genetically influenced declines in the functioning of organs and systems that are universal in all members of our species. Like physical growth, however, biological aging varies widely across parts of the body, and individual differences are great—variation that the lifespan perspective helps us understand. A host of contextual factors—including each person’s genetic makeup, lifestyle, living environment, and historical period—influence biological aging, each of which can accelerate or slow age-related declines (Arking,  2006 ). As a result, the physical changes of the adult years are, indeed, multidimensional and multidirectional (see  page 9  in  Chapter 1 ).

In the following sections, we examine the process of biological aging. Then we turn to physical and motor changes already under way in early adulthood. As you will see, biological aging can be modified substantially through behavioral and environmental interventions. During the twentieth century, improved nutrition, medical treatment, sanitation, and safety added 25 to 30 years to average life expectancy in industrialized nations, a trend that is continuing (see  Chapter 1  page 8 ). We will take up life expectancy in greater depth in  Chapter 17 .

image3 Biological Aging Is Under Way in Early Adulthood

At an intercollegiate tournament, Sharese dashed across the playing field for hours, leaping high to catch Frisbees sailing her way. In her early twenties, she is at her peak in strength, endurance, sensory acuteness, and immune system responsiveness. Yet over the next two decades, she will age and, as she moves into middle and late adulthood, will show more noticeable declines.

Biological aging is the combined result of many causes, some operating at the level of DNA, others at the level of cells, and still others at the level of tissues, organs, and the whole organism. Hundreds of theories exist, indicating that our understanding is incomplete (Arking,  2006 ). For example, one popular idea—the “wear-and-tear”theory—is that the body wears out from use. But no relationship exists between physical activity and early death. To the contrary, regular, moderate-to-vigorous exercise predicts healthier, longer life for people differing widely in SES and ethnicity (Ruiz et al.,  2011 ; Stessman et al.,  2005 ). We now know that this “wear-and-tear”theory is an oversimplification.


This Whitewater kayaker, in his early twenties, is at his peak in strength, endurance, and sensory acuteness.

Aging at the Level of DNA and Body Cells

Current explanations of biological aging at the level of DNA and body cells are of two types: (1) those that emphasize the programmed effects of specific genes and (2) those that emphasize the cumulative effects of random events that damage genetic and cellular material. Support for both views exists, and a combination may eventually prove to be correct.

Genetically programmed aging receives some support from kinship studies indicating that longevity is a family trait. People whose parents had long lives tend to live longer themselves. And greater similarity exists in the lifespans of identical than fraternal twins. But the heritability of longevity is modest, ranging from .15 to .35 for age at death and from .27 to .57 for various measures of current biological age, such as strength of hand grip, respiratory capacity, blood pressure, and bone density (Cevenini et al.,  2008 ; Dutta et al.,  2011 ; Gögele et al.,  2011 ). Rather than inheriting longevity directly, people probably inherit risk and protective factors, which influence their chances of dying earlier or later.

One “genetic programming”theory proposes the existence of “aging genes”that control certain biological changes, such as menopause, gray hair, and deterioration of body cells. The strongest evidence for this view comes from research showing that human cells allowed to divide in the laboratory have a lifespan of 50 divisions, plus or minus 10 (Hayflick,  1998 ). With each duplication, a special type of DNA called  telomeres —located at the ends of chromosomes, serving as a “cap”to protect the ends from destruction—shortens. Eventually, so little remains that the cells no longer duplicate at all. Telomere shortening acts as a brake against somatic mutations (such as those involved in cancer), which become more likely as cells duplicate (Shay & Wright,  2011 ). But an increase in the number of senescent cells (ones with short telomeres) also contributes to age-related disease, loss of function, and earlier mortality (Epel et al.,  2009 ; Shin et al.,  2006 ). As the  Biology and Environment  box on the following page reveals, researchers have begun to identify health behaviors and psychological states that accelerate telomere shortening—powerful biological evidence that certain life circumstances compromise longevity.

Biology and Environment Telomere Length: A Marker of the Impact of Life Circumstances on Biological Aging

In the not-too-distant future, your annual physical exam may include an assessment of the length of your telomeres—DNA at the ends of chromosomes, which safeguard the stability of your cells. Telomeres shorten with each cell duplication; when they drop below a critical length, the cell can no longer divide and becomes senescent (see  Figure 13.1 ). Although telomeres shorten with age, the rate at which they do so varies greatly. An enzyme called telomerase prevents shortening and can even reverse the trend, causing telomeres to lengthen and, thus, protecting the aging cell.

Over the past decade, research examining the influence of life circumstances on telo-mere length has exploded. A well-established finding is that chronic illnesses, such as cardiovascular disease and cancer, hasten telo-mere shortening in white blood cells, which play a vital role in the immune response (see  page 437 ). Telomere shortening, in turn, predicts more rapid disease progression and earlier death (Fuster & Andres,  2006 ).

Accelerated telomere shortening has been linked to a variety of unhealthy behaviors, including cigarette smoking and the physical inactivity and overeating that lead to obesity and to insulin resistance, which often precedes type 2 diabetes (Epel et al.,  2006 ; Gardner et al.,  2005 ). Unfavorable health conditions may alter telomere length as early as the prenatal period, with possible long-term negative consequences for biological aging. In research on rats, poor maternal nutrition during pregnancy resulted in low birth weight and development of shorter telomeres in kidney and heart tissue (Jennings et al.,  1999 ; Tarry-Adkins et al.,  2008 ). In a related human investigation, preschoolers who had been low-birth-weight as infants had shorter telomeres in their white blood cells than did their normal-birth-weight agemates (Raqib et al.,  2007 ).

Persistent psychological stress—in childhood, abuse or bullying; in adulthood, parenting a child with a chronic illness or caring for an elder with dementia—is linked to reduced telomerase activity and telomere shortness in white blood cells (Damjanovic et al.,  2007 ; McEwen,  2007 ; Shalev,  2012 ; Simon et al.,  2006 ). Can stress actually modify telomeres? In a laboratory experiment, researchers exposed human white blood cells to the stress hormone cortisol. The cells responded by decreasing production of telomerase (Choi, Fauce, & Effros,  2008 ).

Fortunately, when adults make positive lifestyle changes, telomeres seem to respond accordingly. In a study of obese women, those who responded to a lifestyle intervention with reduced psychological stress and healthier eating behaviors also displayed gains in telomerase activity (Daubenmier et al.,  2012 ). In another investigation of men varying widely in age, greater maximum vital capacity of the lungs (a measure of physical fitness) was associated with reduced age-related accumulation of senescent white blood cells (Spielmann et al.,  2011 ).

Currently, researchers are working on identifying sensitive periods of telomere change—times when telomeres are most susceptible to modification. Early intervention—for example, enhanced prenatal care and interventions to reduce obesity in childhood—may be particularly powerful. But telomeres are changeable well into late adulthood (Epel et al.,  2009 ). As our understanding of predictors and consequences of telomere length expands, it may become an important index of health and aging throughout life.


FIGURE 13.1 Telomeres at the ends of chromosomes.

(a) Telomeres in a newly created cell. (b) With each cell duplication, telomeres shorten; when too short, they expose DNA to damage, and the cell dies.

According to an alternative, “random events”theory, DNA in body cells is gradually damaged through spontaneous or externally caused mutations. As these accumulate, cell repair and replacement become less efficient, and abnormal cancerous cells are often produced. Animal studies confirm an increase in DNA breaks and deletions and damage to other cellular material with age. Similar evidence is accruing for humans (Freitas & Magalhães,  2011 ).

One hypothesized cause of age-related DNA and cellular abnormalities is the release of  free radicals —naturally occurring, highly reactive chemicals that form in the presence of oxygen.


Kinship studies indicate that longevity is a family trait. In addition to favorable heredity, these grandsons will likely benefit from the model of a fit, active grandfather who buffers stress by enjoying life.

(Radiation and certain pollutants and drugs can trigger similar effects.) When oxygen molecules break down within the cell, the reaction strips away an electron, creating a free radical. As it seeks a replacement from its surroundings, it destroys nearby cellular material, including DNA, proteins, and fats essential for cell functioning. Free radicals are thought to be involved in more than 60 disorders of aging, including cardiovascular disease, neurological disorders, cancer, cataracts, and arthritis (Cutler & Mattson,  2006 ; Stohs,  2011 ). Although our bodies produce substances that neutralize free radicals, some harm occurs, and it accumulates over time.

Some researchers believe that genes for longevity work by defending against free radicals. In support of this view, animal species with longer life expectancies tend to display slower rates of free-radical damage to DNA (Sanz, Pamplona, & Barja,  2006 ). But contrary evidence also exists. Experimental manipulation of the mouse genome, by either augmenting or deleting antioxidant genes, has no impact on longevity. And scientists have identified a cave-dwelling salamander with exceptional longevity—on average, 68 years, making it the longest-living amphibian—with no unusual genetic defenses against free-radical damage (Speakman & Selman,  2011 ).

Research suggests that foods low in saturated fat and rich in vitamins can forestall free-radical damage (Bullo, Lamuela-Raventos, & Salas-Salvado,  2011 ). Nevertheless, the role of free radicals in aging is controversial.

Aging at the Level of Tissues and Organs

What consequences might age-related DNA and cellular deterioration have for the overall structure and functioning of organs and tissues? There are many possibilities. Among those with clear support is the  cross-linkage theory of aging.  Over time, protein fibers that make up the body’s connective tissue form bonds, or links, with one another. When these normally separate fibers cross-link, tissue becomes less elastic, leading to many negative outcomes, including loss of flexibility in the skin and other organs, clouding of the lens of the eye, clogging of arteries, and damage to the kidneys. Like other aspects of aging, cross-linking can be reduced by external factors, including regular exercise and a healthy diet (Kragstrup, Kjaer, & Mackey,  2011 ; Wickens,  2001 ).

Gradual failure of the endocrine system, which produces and regulates hormones, is yet another route to aging. An obvious example is decreased estrogen production in women, which culminates in menopause. Because hormones affect many body functions, disruptions in the endocrine system can have widespread effects on health and survival. For example, a gradual drop in growth hormone (GH) is associated with loss of muscle and bone mass, addition of body fat, thinning of the skin, and decline in cardiovascular functioning. In adults with abnormally low levels of GH, hormone therapy can slow these symptoms, but it has serious side effects, including increased risk of fluid retention in tissues, muscle pain, and cancer (Harman & Blackman,  2004 ; Ceda et al.,  2010 ). So far, diet and physical activity are safer ways to limit these aspects of biological aging.

Finally, declines in immune system functioning contribute to many conditions of aging, including increased susceptibility to infectious disease and cancer and changes in blood vessel walls associated with cardiovascular disease. Decreased vigor of the immune response seems to be genetically programmed, but other aging processes we have considered (such as weakening of the endocrine system) can intensify it (Alonso-Férnandez & De la Fuente,  2011 ; Hawkley & Cacioppo,  2004 ). Indeed, combinations of theories—the ones just reviewed as well as others—are needed to explain the complexities of biological aging. With this in mind, let’s turn to physical signs and other characteristics of aging.

image7 Physical Changes

During the twenties and thirties, changes in physical appearance and declines in body functioning are so gradual that most are hardly noticeable. Later, they will accelerate. The physical changes of aging are summarized in  Table 13.1 . We will examine several in detail here and take up others in later chapters. Before we begin, let’s note that these trends are derived largely from cross-sectional studies. Because younger cohorts have experienced better health care and nutrition, cross-sectional evidence can exaggerate impairments associated with aging. Fortunately, longitudinal evidence is expanding, helping to correct this picture.

Cardiovascular and Respiratory Systems

During her first month in graduate school, Sharese pored over research articles on cardiovascular functioning. In her African-American extended family, her father, an uncle, and three aunts had died of heart attacks in their forties and fifties. These tragedies prompted Sharese to enter the field of public health in hopes of finding ways to relieve health problems among black Americans. Hypertension, or high blood pressure, occurs 12 percent more often in the U.S. black than in the U.S. white population; the rate of death from heart disease among African Americans is 30 percent higher (American Heart Association,  2012 ).

TABLE 13.1 Physical Changes of Aging

    Vision From age 30 As the lens stiffens and thickens, ability to focus on close objects declines. Yellowing of the lens, weakening of muscles controlling the pupil, and clouding of the vitreous (gelatin-like substance that fills the eye) reduce light reaching the retina, impairing color discrimination and night vision. Visual acuity, or fineness of discrimination, decreases, with a sharp drop between ages 70 and 80.
    Hearing From age 30 Sensitivity to sound declines, especially at high frequencies but gradually extending to all frequencies. Change is more than twice as rapid for men as for women.
    Taste From age 60 Sensitivity to the four basic tastes—sweet, salty, sour, and bitter—is reduced. This may be due to factors other than aging, since number and distribution of taste buds do not change.
    Smell From age 60 Loss of smell receptors reduces ability to detect and identify odors.
    Touch Gradual Loss of touch receptors reduces sensitivity on the hands, particularly the fingertips.
Cardiovascular Gradual As the heart muscle becomes more rigid, maximum heart rate decreases, reducing the heart’s ability to meet the body’s oxygen requirements when stressed by exercise. As artery walls stiffen and accumulate plaque, blood flow to body cells is reduced.
Respiratory Gradual Under physical exertion, respiratory capacity decreases and breathing rate increases. Stiffening of connective tissue in the lungs and chest muscles makes it more difficult for the lungs to expand to full volume.
Immune Gradual Shrinking of the thymus limits maturation of T cells and disease-fighting capacity of B cells, impairing the immune response.
Muscular Gradual As nerves stimulating them die, fast-twitch muscle fibers (responsible for speed and explosive strength) decline in number and size to a greater extent than slow-twitch fibers (which support endurance). Tendons and ligaments (which transmit muscle action) stiffen, reducing speed and flexibility of movement.
Skeletal Begins in the late thirties, accelerates in the fifties, slows in the seventies Cartilage in the joints thins and cracks, leading bone ends beneath it to erode. New cells continue to be deposited on the outer layer of the bones, and mineral content of bone declines. The resulting broader but more porous bones weaken the skeleton and make it more vulnerable to fracture. Change is more rapid in women than in men.
Reproductive In women, accelerates after age 35; in men, begins after age 40 Fertility problems (including difficulty conceiving and carrying a pregnancy to term) and risk of having a baby with a chromosomal disorder increase.
Nervous From age 50 Brain weight declines as neurons lose water content and die, mostly in the cerebral cortex, and as ventricles (spaces) within the brain enlarge. Development of new synapses and limited generation of new neurons can, in part, compensate for these declines.
Skin Gradual Epidermis (outer layer) is held less tightly to the dermis (middle layer); fibers in the dermis and hypodermis (inner layer) thin; fat cells in the hypodermis decline. As a result, the skin becomes looser, less elastic, and wrinkled. Change is more rapid in women than in men.
Hair From age 35 Grays and thins.
Height From age 50 Loss of bone strength leads to collapse of disks in the spinal column, leading to a height loss of as much as 2 inches by the seventies and eighties.
Weight Increases to age 50; declines from age 60 Weight change reflects a rise in fat and a decline in muscle and bone mineral. Since muscle and bone are heavier than fat, the resulting pattern is weight gain followed by loss. Body fat accumulates on the torso and decreases on the extremities.

Sources: Arking, 2006; Lemaitre et al., 2012; Whitbourne, 1996.

Sharese was surprised to learn that fewer age-related changes occur in the heart than we might expect, given that heart disease is a leading cause of death throughout adulthood, responsible for as many as 10 percent of U.S. male and 5 percent of U.S. female deaths between ages 20 and 34—figures that more than double in the following decade and, thereafter, continue to rise steadily with age (American Heart Association,  2012 ). In healthy individuals, the heart’s ability to meet the body’s oxygen requirements under typical conditions (as measured by heart rate in relation to volume of blood pumped) does not change during adulthood. Only during stressful exercise does heart performance decline with age—a change due to a decrease in maximum heart rate and greater rigidity of the heart muscle (Arking,  2006 ). Consequently, the heart has difficulty delivering enough oxygen to the body during high activity and bouncing back from strain.

One of the most serious diseases of the cardiovascular system is atherosclerosis, in which heavy deposits of plaque containing cholesterol and fats collect on the walls of the main arteries. If present, it usually begins early in life, progresses during middle adulthood, and culminates in serious illness. Atherosclerosis is multiply determined, making it hard to separate the contributions of biological aging from individual genetic and environmental influences. The complexity of causes is illustrated by research indicating that before puberty, a high-fat diet produces only fatty streaks on the artery walls (Oliveira, Patin, & Escrivao,  2010 ). In sexually mature adults, however, it leads to serious plaque deposits, suggesting that sex hormones may heighten the insults of a high-fat diet.

Heart disease has decreased considerably since the mid-twentieth century, with a larger drop in the last 25 years due to a decline in cigarette smoking, to improved diet and exercise among at-risk individuals, and to better medical detection and treatment of high blood pressure and cholesterol (American Heart Association,  2012 ). And as a longitudinal follow-up of an ethnically diverse sample of U.S. black and white 18- to 30-year-olds revealed, those at low risk—defined by not smoking, normal body weight, healthy diet, and regular physical activity—were far less likely to be diagnosed with symptoms of heart disease over the succeeding two decades (Liu et al.,  2012 ). Later, when we consider health and fitness, we will see why heart attacks were so common in Sharese’s family—and why they occur at especially high rates in the African-American population.

Like the heart, the lungs show few age-related changes in functioning at rest, but during physical exertion, respiratory volume decreases and breathing rate increases with age. Maximum vital capacity (amount of air that can be forced in and out of the lungs) declines by 10 percent per decade after age 25 (Mahanran et al.,  1999 ; Wilkie et al.,  2012 ). Connective tissue in the lungs, chest muscles, and ribs stiffens with age, making it more difficult for the lungs to expand to full volume (Smith & Cotter,  2008 ). Fortunately, under normal conditions, we use less than half our vital capacity. Nevertheless, aging of the lungs contributes to older adults’ difficulty in meeting the body’s oxygen needs while exercising.

Motor Performance

Declines in heart and lung functioning under conditions of exertion, combined with gradual muscle loss, lead to changes in motor performance. In most people, the impact of biological aging on motor skills is difficult to separate from decreases in motivation and practice. Therefore, researchers study competitive athletes, who try to attain their very best performance in real life (Tanaka & Seals,  2003 ). As long as athletes continue intensive training, their attainments at each age approach the limits of what is biologically possible.

Many athletic skills peak between ages 20 and 35, then gradually decline. In several investigations, the mean ages for best performance of Olympic and professional athletes in a variety of sports were charted over time. Absolute performance in most events improved over the past century. Athletes continually set new world records, suggesting improved training methods. But ages of best performance remained relatively constant. Athletic tasks that require speed of limb movement, explosive strength, and gross-motor coordination—sprinting, jumping, and tennis—typically peak in the early twenties. Those that depend on endurance, arm–hand steadiness, and aiming—long-distance running, baseball, and golf—usually peak in the late twenties and early thirties (Bradbury,  2009 ; Schulz & Curnow,  1988 ). Because these skills require either stamina or precise motor control, they take longer to perfect.

Research on outstanding athletes tells us that the upper biological limit of motor capacity is reached in the first part of early adulthood. How quickly do athletic skills weaken in later years? Longitudinal research on master runners reveals that as long as practice continues, speed drops only slightly from the mid-thirties into the sixties, when performance falls off at an accelerating pace (see  Figure 13.2 ) (Tanaka & Seals,  2003 ; Trappe,  2007 ). In the case of long-distance swimming—a non-weight-bearing exercise with a low incidence of injury—the decline in speed is even more gradual: The accelerating performance drop-off is delayed until the seventies (Tanaka & Seals,  1997 ).


In her early thirties, professional tennis champion Serena Williams recently became the oldest player to be ranked World No. 1 in the history of the Women’s Tennis Association. Sustained training leads to adaptations in body structures that minimize motor decline into the sixties.


FIGURE 13.2 Ten-kilometer running times with advancing age, based on longitudinal performances of hundreds of master athletes.

Runners maintain their speed into the mid-thirties, followed by modest increases in running times into the sixties, with a progressively steeper increase thereafter.

(From H. Tanaka & D. R. Seals, 2003, “Dynamic Exercise Performance in Masters Athletes: Insight into the Effects of Primary Human Aging on Physiological Functional Capacity,” Journal of Applied Physiology, 5, p. 2153. © The American Physiological Society (APS). All rights reserved. Adapted with permission.)

Indeed, sustained training leads to adaptations in body structures that minimize motor declines. For example, vital capacity is one-third greater in both younger and older people who participate actively in sports than in healthy inactive age-mates (Pimentel et al.,  2003 ; Zaccagni, Onisto, & Gualdi-Russo,  2009 ). Training also slows muscle loss, increases speed and force of muscle contraction, and leads fast-twitch muscle fibers to be converted into slow-twitch fibers, which support excellent long-distance running performance and other endurance skills (Faulkner et al.,  2007 ). In a study of hundreds of thousands of amateur marathon competitors, 25 percent of the 65- to 69-year-old runners were faster than 50 percent of the 20- to 54-year-old runners (Leyk et al.,  2010 ). Yet many of the older runners had begun systematic marathon training only in the past five years.

In sum, although athletic skills are at their best in early adulthood, biological aging accounts for only a small part of age-related declines until advanced old age. Lower levels of performance by healthy people into their sixties and seventies largely reflect reduced capacities resulting from adaptation to a less physically demanding lifestyle.

Immune System

The immune response is the combined work of specialized cells that neutralize or destroy antigens (foreign substances) in the body. Two types of white blood cells play vital roles. T cells, which originate in the bone marrow and mature in the thymus (a small gland located in the upper part of the chest), attack antigens directly. B cells, manufactured in the bone marrow, secrete antibodies into the bloodstream that multiply, capture antigens, and permit the blood system to destroy them. Because receptors on their surfaces recognize only a single antigen, T and B cells come in great variety. They join with additional cells to produce immunity.

The capacity of the immune system to offer protection against disease increases through adolescence and declines after age 20. The trend is partly due to changes in the thymus, which is largest during the teenage years, then shrinks until it is barely detectable by age 50. As a result, production of thymic hormones is reduced, and the thymus is less able to promote full maturity and differentiation of T cells (Fülöp et al.,  2011 ). Because B cells release far more antibodies when T cells are present, the immune response is compromised further.

Withering of the thymus is not the only reason that the body gradually becomes less effective in warding off illness. The immune system interacts with the nervous and endocrine systems. For example, psychological stress can weaken the immune response. During final exams, for example, Sharese was less resistant to colds. And in the month after her father died, she had great difficulty recovering from the flu. Conflict-ridden relationships, caring for an ill aging parent, sleep deprivation, and chronic depression can also reduce immunity (Fagundes et al.,  2011 ; Robles & Carroll,  2011 ). And physical stress—from pollution, allergens, poor nutrition, and rundown housing—undermines immune functioning throughout adulthood (Friedman & Lawrence,  2002 ). When physical and psychological stressors combine, the risk of illness is magnified.

The link between stress and illness makes sense when we consider that stress hormones mobilize the body for action, whereas the immune response is fostered by reduced activity. But this also means that increased difficulty coping with physical and psychological stress can contribute to age-related declines in immune system functioning.

Reproductive Capacity

Sharese was born when her mother was in her early twenties. At the same age a generation later, Sharese was still single and entering graduate school. Many people believe that pregnancy during the twenties is ideal, not only because of lower risk of miscarriage and chromosomal disorders (see  Chapter 2 ) but also because younger parents have more energy to keep up with active children. Nevertheless, as  Figure 13.3 on  page 438  reveals, first births to women in their thirties have increased greatly over the past three decades. Many people are delaying childbearing until their education is complete, their careers are well-established, and they know they can support a child.

Nevertheless, reproductive capacity does decline with age. Between ages 15 and 29, 11 percent of U.S. married childless women report fertility problems, a figure that rises to 14 percent among 30- to 34-year-olds and to over 40 percent among 35-to 44-year-olds, when the success of reproductive technologies drops sharply (see  page 54  in  Chapter 2 ) (U.S. Department of Health and Human Services,  2012b ). Because the uterus shows no consistent changes from the late thirties through the forties, the decline in female fertility is largely due to reduced number and quality of ova. In many mammals, including humans, a certain level of reserve ova in the ovaries is necessary for conception (Balasch,  2010 ; Djahanbakhch, Ezzati, & Zosmer,  2007 ). Some women have normal menstrual cycles but do not conceive because their reserve of ova is too low.


FIGURE 13.3 First births to American women of different ages in 1970 and 2010.

The birthrate decreased during this period for women 20 to 24 years of age, whereas it increased for women 25 years of age and older. For women in their thirties, the birthrate increased six-fold, and for those in their early forties, it doubled. Similar trends have occurred in other industrialized nations. (From U.S. Census Bureau, 2012b.)

In males, semen volume, sperm motility, and percentage of normal sperm decrease gradually after age 35, contributing to reduced fertility rates in older men (Lambert, Masson, & Fisch,  2006 ). Although there is no best time in adulthood to begin parenthood, individuals who postpone childbearing until their late thirties or their forties risk having fewer children than they desired or none at all.


REVIEW How does research on life conditions that accelerate telomere shortening illustrate the concept of epigenesis, discussed in  Chapter 2  (see  pages 73  75 )?

CONNECT How do heredity and environment jointly contribute to age-related changes in cardiovascular, respiratory, and immune system functioning?

APPLY Penny is a long-distance runner for her college track team. What factors will affect Penny’s running performance 30 years from now?

REFLECT Before reading this chapter, had you thought of early adulthood as a period of aging? Why is it important for young adults to be aware of influences on biological aging?

image11 Health and Fitness

Figure 13.4  displays leading causes of death in early adulthood in the United States. Death rates for all causes exceed those of other industrialized nations (OECD,  2012b ). The difference is likely due to a combination of factors, including higher rates of poverty and extreme obesity, more lenient gun-control policies, and historical lack of universal health insurance in the United States. In later chapters, we will see that homicide rates decline with age, while disease and physical disability rates rise. Biological aging clearly contributes to this trend. But, as we have noted, wide individual and group differences in physical changes are linked to environmental risks and health-related behaviors.

SES variations in health over the lifespan reflect these influences. With the transition from childhood to adulthood, health inequalities associated with SES increase; income, education, and occupational status show strong, continuous relationships with almost every disease and health indicator (Braveman et al.,  2010 ; Smith & Infurna,  2011 ). Furthermore, SES largely accounts for the sizable health advantage of white over ethnic minority adults in the United States (Phuong, Frank, & Finch,  2012 ). Consequently, improving socioeconomic conditions is essential for closing ethnic gaps in health.


FIGURE 13.4 Leading causes of death between 25 and 44 years of age in the United States.

Nearly half of unintentional injuries are motor vehicle accidents. As later chapters will reveal, unintentional injuries remain a leading cause of death at older ages, rising sharply in late adulthood. Rates of cancer and cardiovascular disease rise steadily during middle and late adulthood. (Adapted from U.S. Department of Health and Human Services, 2011b.)

Health-related circumstances and habits—stressful life events, crowding, pollution, diet, exercise, overweight and obesity, substance abuse, jobs with numerous health risks, availability of supportive social relationships, and (in the United States) access to affordable health care—underlie SES health disparities (Ertel, Glymour, & Berkman,  2009 ; Smith & Infurna,  2011 ). Furthermore, poor health in childhood, which is linked to low SES, affects health in adulthood. The overall influence of childhood factors lessens if SES improves. But in most instances, child and adult SES remain fairly consistent, exerting a cumulative impact that amplifies SES differences in health with age (Herd, Robert, & House,  2011 ).

Why are SES variations in health and mortality larger in the United States than in other industrialized nations? Besides lack of universal health insurance, low-income and poverty-stricken U.S. families are financially less well-off than families classified in these ways in other countries (Wilkinson & Pickett,  2006 ). In addition, SES groups are more likely to be segregated by neighborhood in the United States, resulting in greater inequalities in environmental factors that affect health, such as housing, pollution, education, and community services.

These findings reveal, once again, that the living conditions that nations and communities provide combine with those that people create for themselves to affect physical aging. Because the incidence of health problems is much lower during the twenties and thirties than later on, early adulthood is an excellent time to prevent later problems. In the following sections, we take up a variety of major health concerns—nutrition, exercise, substance abuse, sexuality, and psychological stress.


Bombarded with advertising claims and an extraordinary variety of food choices, adults find it increasingly difficult to make wise dietary decisions. An abundance of food, combined with a heavily scheduled life, means that most Americans eat because they feel like it or because it is time to do so rather than to maintain the body’s functions (Donatelle,  2012 ). As a result, many eat the wrong types and amounts of food. Overweight and obesity and a high-fat diet are widespread nutritional problems with long-term consequences for adult health.

Overweight and Obesity.

In  Chapter 9 , we noted that obesity (a greater than 20 percent increase over average body weight, based on age, sex, and physical build) has increased dramatically in many Western nations, and it is on the rise in the developing world as well. Among adults, a body mass index (BMI) of 25 to 29 constitutes overweight, a BMI of 30 or greater (amounting to 30 or more excess pounds) constitutes obesity. Today, 36 percent of U.S. adults are obese. The rate rises to 38 percent among Hispanics, 39 percent among Native Americans, and 50 percent among African Americans (Flegal et al.,  2012 ). The overall prevalence of obesity is similar among men and women.

Overweight—a less extreme but nevertheless unhealthy condition—affects an additional 33 percent of Americans. Combine the rates of overweight and obesity and the total, 69 percent, makes Americans the heaviest people in the world.  TAKE A MOMENT…  Notice in these figures that the U.S. obesity rate now exceeds its rate of overweight, a blatant indicator of the growing severity of the problem.

Recall from  Chapter 9  that overweight children are very likely to become overweight adults. But a substantial number of people show large weight gains in adulthood, most often between ages 25 and 40. And young adults who were already overweight or obese typically get heavier, leading obesity rates to rise steadily between ages 20 and 65 (Flegel et al., 2012).

Causes and Consequences.

As noted in  Chapter 9 , heredity makes some people more vulnerable to obesity than others. But environmental pressures underlie the rising rates of obesity in industrialized nations: With the decline in need for physical labor in the home and workplace, our lives have become more sedentary. Meanwhile, the average number of calories and amount of sugar and fat consumed by Americans rose over most of the twentieth and early twenty-first century, with a sharp increase after 1970 (see the  Social Issues: Health box on  pages 440  441 ).

Adding some weight between ages 25 and 50 is a normal part of aging because  basal metabolic rate (BMR), the amount of energy the body uses at complete rest, gradually declines as the number of active muscle cells (which create the greatest energy demand) drops off. But excess weight is strongly associated with serious health problems (see  page 291  in  Chapter 9 )—including type 2 diabetes, heart disease, and many forms of cancer—and with early death.


SES variations in health in the United States—larger than in other industrialized nations—are in part due to lack of access to affordable health care. This Los Angeles free clinic helps address the problem by offering preventive services, including eye exams, to over 1,200 patients per day.

Furthermore, overweight adults suffer enormous social discrimination. Compared with their normal-weight agemates, they are less likely to find mates, be rented apartments, receive financial aid for college, or be offered jobs. And they report frequent mistreatment by family members, peers, co-workers, and health professionals (Ickes,  2011 ; Puhl, Heuer, & Brownell,  2010 ). Since the mid-1990s, discrimination experienced by overweight Americans has increased, with serious physical and mental health consequences. Weight stigma triggers anxiety, depression, and low self-esteem, which increase the chances that that unhealthy eating behaviors will persist and even worsen (Puhl & Heuer,  2010 ). The widespread but incorrect belief, perpetuated by the media, that obesity is a personal choice promotes negative stereotyping of obese persons.

Social Issues: Health The Obesity Epidemic: how Americans Became the Heaviest People in the World

In the late 1980s, obesity in the United States started to soar. As the maps in  Figure 13.5  show, it quickly engulfed the nation and has continued to expand. The epidemic also spread to other Western nations and, more recently, to developing countries. For example, as noted in  Chapter 9 , obesity was rare in China 30 years ago, but today it affects 7 percent of Chinese children and adolescents and 11 percent of adults; an additional 15 percent of the Chinese population is overweight (Xi et al.,  2012 ). Yet China is a low-prevalence country! Worldwide, overweight afflicts more than 1.4 billion adults, 500 million of whom are obese. American Samoa leads the globe in overweight and obesity, with a staggering 94 percent of people affected (World Health Organization,  2013a ). Among industrialized nations, no country matches the United States in prevalence of this life-threatening condition.

A Changing Food Environment and Lifestyle

Several societal factors have encouraged widespread rapid weight gain:

· ● Availability of cheap commercial fat and sugar. The 1970s saw two massive changes in the U.S. food economy: (1) the discovery and mass production of high-fructose corn syrup, a sweetener six times as sweet as ordinary sugar and therefore far less expensive; and (2) the importing from Malaysia of large quantities of palm oil, which is lower in cost than other vegetable oils and also tastier because of its high saturated fat content. Use of corn syrup and palm oil in soft drinks and calorie-dense convenience foods lowered production costs for these items, launching a new era of “cheap, abundant, and tasty calories”(Critser,  2003 ).

· ● Portion supersizing. Fast-food chains discovered a successful strategy for attracting customers: increasing portion sizes substantially and prices just a little for foods that had become inexpensive to produce. Customers thronged to buy “value meals,”jumbo burgers and burritos, and 20-ounce Cokes (Critser,  2003 ). Research reveals that when presented with larger portions, individuals 2 years and older increase their intake, on average, by 25 to 30 percent (Fisher, Rolls, & Birch,  2003 ; Steenhuis & Vermeer,  2009 ).

· ● Increasingly busy lives. Between the 1970s and 1990s, women entered the labor force in record numbers, and the average amount of time Americans worked increased dramatically. Today, 86 percent of employed U.S. men and 66 percent of employed women work over 40 hours per week—substantially more than in most other countries (Schor,  2002 ; United Nations,  2012 ). As time for meal preparation shrank, eating out increased (Midlin, Jenkins, & Law,  2009 ). In addition, Americans became frequent snackers, tempted by a growing assortment of high-calorie snack foods on supermarket shelves. And the number of calories Americans consumed away from home doubled, with dietary fat increasing from 19 to 38 percent (Nielsen & Popkin,  2003 ).

· ● Declining rates of physical activity. During the 1980s, physical activity, which had risen since the 1960s, started to fall as Americans spent more time in sedentary transportation and jobs—driving to and from work and sitting throughout the work day, often behind a computer. At home, a rise in TV viewing to an average of more than four hours per day has been linked to weight gain in adults and children alike (Foster, Gore, & West,  2006 ).

Combating the Obesity Epidemic

· Obesity is responsible for $150 billion in health expenditures and an estimated 300,000 premature deaths per year in the United States alone (Finkelstein et al.,  2009 ; Flegal et al.,  2007 ). Because multiple social and economic influences have altered the environment to promote this epidemic, broad societal efforts are needed to combat it. Effective policies include

· ● Government funding to support massive public education efforts about healthy eating and physical activity

· ● A high priority placed on building parks and recreation centers and replacing unhealthy fast-food outlets with access to healthy, affordable foods in low-income neighborhoods, where overweight and obesity are highest

· ● Laws that mandate prominent posting of the calorie, sugar, and fat content of foods sold in restaurants, movie theaters, and convenience stores

· ● Incentives to schools and workplaces for promoting healthy eating and daily exercise and for offering weight-management programs

· ● Increased obesity-related medical coverage in government-sponsored health insurance programs for low-income families image14

FIGURE 13.5Obesity trends among U.S. adults, 1990 and 2011.

The maps show that obesity has increased sharply. In 2011, twelve states (Alabama, Arkansas, Indiana, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Oklahoma, South Carolina, Texas, and West Virginia) had rates equal to or greater than 30 percent.

(From Centers for Disease Control and Prevention, 2012a.)


· Because obesity climbs in early and middle adulthood, treatment for adults should begin as soon as possible—preferably in the early twenties. Even moderate weight loss reduces health problems substantially (Poobalan et al.,  2010 ). But successful intervention is difficult. Most individuals who start a weight-loss program return to their original weight, and often to a higher weight, within two years (Vogels, Diepvens, & Westerterp-Plantenga,  2005 ). The high rate of failure is partly due to limited evidence on just how obesity disrupts the complex neural, hormonal, and metabolic factors that maintain a normal body-weight set point. Until more information is available, researchers are examining the features of treatments and participants associated with greater success. The following elements promote lasting behavior change:

· ● A lifestyle change to a nutritious diet lower in calories, sugar, and fat, plus regular exercise. To lose weight, Sharese sharply reduced calories, sugar, and fat in her diet and exercised regularly. The precise balance of dietary protein, carbohydrates, and fats that best helps adults lose weight is a matter of heated debate. Although scores of diet books offer different recommendations, no clear-cut evidence exists for the long-term superiority of one approach over others (Tsai & Wadden,  2005 ).

· Research does confirm that a permanent lifestyle alteration that restricts calorie intake and fat (to no more than 20 to 30 percent of calories) and that increases physical activity is essential for reducing the impact of a genetic tendency toward overweight. But most people mistakenly believe that only temporary lifestyle changes are needed (MacLean et al.,  2011 ).

· ● Training participants to keep an accurate record of food intake and body weight. About 30 to 35 percent of obese people sincerely believe they eat less than they do. And although they have continued to gain weight, American adults generally report weight losses—suggesting that they are in denial about the seriousness of their weight condition (Wetmore & Mokdad, 2012). Furthermore, from 25 to 45 percent report problems with binge eating—a behavior associated with weight-loss failure (Blaine & Rodman,  2007 ). As Sharese recognized how often she ate when not actually hungry and regularly recorded her weight, she was better able to limit food intake.

· ● Social support. Group or individual counseling and encouragement from friends and relatives help sustain weight-loss efforts by fostering self-esteem and self-efficacy (Poobalan et al.,  2010 ). Once Sharese decided to act, with the support of her family and a weight-loss counselor, she felt better about herself even before the first pounds were shed.

· ● Teaching problem-solving skills. Most overweight adults do not realize that because their body has adapted to over-weight, difficult periods requiring high self-control and patience are inevitable in successful weight loss (MacLean et al.,  2011 ). Acquiring cognitive and behavioral strategies for coping with tempting situations and periods of slowed progress is associated with long-term change (Cooper & Fairburn,  2002 ). Weight-loss maintainers are more likely than individuals who relapse to be conscious of their behavior, to use social support, and to confront problems directly.

· ● Extended intervention. Longer treatments (from 25 to 40 weeks) that include the components listed here grant people time to develop new habits.

Although many Americans on weight-reduction diets are overweight, about one-third of dieters are within normal range (Mokdad et al.,  2001 ). Recall from  Chapter 11  that the high value placed on thinness creates unrealistic expectations about desirable body weight and contributes to anorexia and bulimia, dangerous eating disorders that remain common in early adulthood (see  pages 372  373 ). Throughout adulthood, both underweight and obesity are associated with increased mortality (Ringbäck, Eliasson, & Rosén,  2008 ). A sensible body weight—neither too low nor too high—predicts physical and psychological health and longer life.


A permanent lifestyle change that includes an increase in physical activity is essential for treating obesity.

Dietary Fat.

During college, Sharese altered the diet of her childhood and adolescent years, sharply limiting red meat, eggs, butter, and fried foods. U.S. national dietary recommendations include reducing fat to 30 percent of total caloric intake, with no more than 7 percent made up of saturated fat, which generally comes from meat and dairy products and is solid at room temperature (U.S. Department of Agriculture,  2011a ). Many researchers believe that dietary fat plays a role in the age-related rise in breast cancer and (when it includes large amounts of red meat) is linked to colon cancer (Ferguson,  2010 ; Turner,  2011 ). But the main reasons for limiting dietary fat are the strong connection of total fat with obesity and of saturated fat with cardiovascular disease (Hooper et al.,  2012 ). Nevertheless, despite a slight drop in fat consumption, most American adults eat too much.

Moderate fat consumption is essential for normal body functioning. But when we consume too much fat, especially saturated fat, some is converted to cholesterol, which accumulates as plaque on the arterial walls in atherosclerosis. Earlier in this chapter, we noted that atherosclerosis is determined by multiple biological and environmental factors. But excess fat consumption (along with other societal conditions) is an important contributor to the high rate of heart disease in the U.S. black population. As  Figure 13.6 shows, when researchers compared Africans in West Africa, the Caribbean, and the United States (the historic path of the slave trade), dietary fat increased, and so did high blood pressure and heart disease (Luke et al.,  2001 ).

The best rule of thumb is to eat less fat of all kinds, replacing saturated fat with unsaturated fat (which is derived from vegetables or fish and is liquid at room temperature) and with complex carbohydrates (whole grains, fruits, and vegetables), which are beneficial to cardiovascular health and protective against colon cancer (Kaczmarczyk, Miller, & Freund,  2012 ). Furthermore, regular exercise can reduce the harmful influence of saturated fat because it creates chemical byproducts that help eliminate cholesterol from the body.


FIGURE 13.6 Dietary fat and prevalence of high blood pressure among Africans in West Africa, the Caribbean, and the United States.

The three regions represent the historic path of the slave trade and, therefore, have genetically similar populations. As dietary fat increases, high blood pressure and heart disease rise. Both are particularly high among African Americans. (Adapted from Luke et al., 2001.)


Three times a week, over the noon hour, Sharese delighted in running, making her way to a wooded trail that cut through a picturesque area of the city. Regular exercise kept her fit and slim, and she noticed that she caught fewer respiratory illnesses than in previous years, when she had been sedentary and overweight. As Sharese explained to a friend, “Exercise gives me a positive outlook and calms me down. Afterward, I feel a burst of energy that gets me through the day.”

Although most Americans are aware of the health benefits of exercise, only 47 percent engage in the nationally recommended 150 minutes per week of at least moderately intense leisure-time physical activity. And just 24 percent engage in the recommended two sessions per week of resistance exercises, which place a moderately stressful load on each of the major muscle groups. Over half of Americans are inactive, with no regular brief sessions of even light activity (U.S. Department of Health and Human Services,  2011c ). More women than men are inactive. And inactivity is greater among low-SES adults, who live in less safe neighborhoods, have more health problems, experience less social support for exercising regularly, and feel less personal control over their health.


Contact your local parks and recreation department to find out what community supports and services exist to increase adult physical activity. Are any special efforts made to reach low-SES adults?

Besides reducing body fat and building muscle, exercise fosters resistance to disease. Frequent bouts of moderate-intensity exercise enhance the immune response, lowering the risk of colds or flu and promoting faster recovery from these illnesses (Donatelle,  2012 ). Furthermore, animal and human evidence indicates that physical activity is linked to reduced incidence of several types of cancer, with the strongest findings for breast and colon cancer (Anzuini, Battistella, & Izzotti,  2011 ). Physically active people are also less likely to develop diabetes and cardiovascular disease (Bassuk & Manson,  2005 ). If they do, these illnesses typically occur later and are less severe than among their inactive agemates.

How does exercise help prevent these serious illnesses? First, it reduces the incidence of obesity—a risk factor for heart disease, diabetes, and cancer. In addition, people who exercise probably adopt other healthful behaviors, thereby lowering the risk of diseases associated with high-fat diets, alcohol consumption, and smoking. In animal studies, exercise directly inhibits growth of cancerous tumors—beyond the impact of diet, body fat, and the immune response (de Lima et al.,  2008 ). Exercise also promotes cardiovascular functioning by strengthening the heart muscle, decreasing blood pressure, and producing a form of “good cholesterol”(high-density lipoproteins, or HDLs) that helps remove “bad cholesterol”(low-density lipoproteins, or LDLs) from the artery walls (Donatelle,  2012 ).


Regular exercise of at least moderate intensity predicts a healthier, longer life. Participants in this kickboxing class reap both physical and mental health benefits.

Yet another way that exercise guards against illness is through its mental health benefits. Physical activity reduces anxiety and depression and improves mood, alertness, and energy. Furthermore, EEG and fMRI evidence indicates that exercise enhances neural activity in the cerebral cortex, and it improves overall cognitive functioning (Carek, Laibstain, & Carek,  2011 ; Etnier & Labban,  2012 ; Hillman, Erickson, & Kramer,  2008 ). The impact of exercise on a “positive outlook,”as Sharese expressed it, is most obvious just after a workout and can last for several hours (Acevedo,  2012 ). The stress-reducing properties of exercise undoubtedly strengthen immunity to disease. And as physical activity enhances cognitive functioning and psychological well-being, it promotes on-the-job productivity, self-esteem, ability to cope with stress, and life satisfaction.

When we consider the evidence as a whole, it is not surprising that physical activity is associated with substantially lower death rates from all causes. The contribution of exercise to longevity cannot be accounted for by preexisting illness in inactive people. In a Danish longitudinal study of a nationally representative sample of 7,000 healthy 20- to 79-year-olds followed over several decades, mortality was lower among those who increased their leisure-time physical activity from low to either moderate or high than among those who remained consistently inactive (Schnohr, Scharling, & Jensen,  2003 ).

How much exercise is recommended for a healthier, happier, and longer life? Moderately intense physical activity—for example, 30 minutes of brisk walking—on most days leads to health benefits for previously inactive people. Adults who exercise at greater intensity—enough to build up a sweat—derive even greater protection (American College of Sports Medicine,  2011 ). Regular, vigorous exercisers show large reductions in risk of cardiovascular disease, diabetes, colon cancer, and obesity.

Substance Abuse

Alcohol and drug use peaks among U.S. 19- to 25-year-olds and then declines steadily with age. Eager to try a wide range of experiences before settling down to the responsibilities of adulthood, young people of this age are more likely than younger or older individuals to smoke cigarettes, chew tobacco, use marijuana, and take stimulants to enhance cognitive or physical performance (U.S. Department of Health and Human Services,  2011e ). Binge drinking, driving under the influence, and experimentation with prescription drugs (such as OxyContin, a highly addictive painkiller) and “party drugs”(such as LSD and MDMA, or Ecstasy) also increase, at times with tragic consequences. Risks include brain damage, lasting impairments in mental functioning, and unintentional injury and death (Montoya et al.,  2002 ; National Institute on Drug Abuse,  2012 ).

Furthermore, when alcohol and drug taking become chronic, they intensify the psychological problems that underlie addiction. As many as 12 percent of 19- to 25-year-old men and 6 percent of women are substance abusers (U.S. Department of Health and Human Services,  2011e ). Return to  Chapter 11  pages 380  381 , to review factors that lead to alcohol and drug abuse in adolescence. The same personal and situational conditions are predictive in the adult years. Cigarette smoking and alcohol consumption are the most commonly abused substances.

Cigarette Smoking.

Dissemination of information on the harmful effects of cigarette smoking has helped reduce its prevalence among U.S. adults from 40 percent in 1965 to 19 percent in 2010 (Centers for Disease Control and Prevention, 2012e). Still, smoking has declined very slowly, and most of the drop is among college graduates, with very little change for those who did not finish high school. Furthermore, although more men than women smoke, the gender gap is much smaller today than in the past, reflecting a sharp increase in smoking among young women who did not finish high school. Smoking among college students has also risen—for students of both sexes and of diverse ethnicities. More than 90 percent of men and 85 percent of women who smoke started before age 21 (U.S. Department of Health and Human Services,  2011e ). And the earlier people start smoking, the greater their daily cigarette consumption and likelihood of continuing, an important reason that preventive efforts with adolescents and young adults are vital.

The ingredients of cigarette smoke—nicotine, tar, carbon monoxide, and other chemicals—leave their damaging mark throughout the body. As smokers inhale, oxygen delivery to tissues is reduced, and heart rate and blood pressure rise. Over time, exposure to toxins and insufficient oxygen result in damage to the retina of the eye; constriction of blood vessels leading to painful vascular disease; skin abnormalities, including premature aging, poor wound healing, and hair loss; decline in bone mass; decrease in reserve ova, uterine abnormalities, and earlier menopause in women; and reduced sperm count and higher rate of sexual impotence in men (Dechanet et al.,  2011 ; Freiman et al.,  2004 ; Thornton et al.,  2005 ). Other deadly outcomes include increased risk of heart attack, stroke, acute leukemia, melanoma, and cancer of the mouth, throat, larynx, esophagus, lungs, stomach, pancreas, kidneys, and bladder.

Cigarette smoking is the single most important preventable cause of death in industrialized nations. One out of every three young people who become regular smokers will die from a smoking-related disease, and the vast majority will suffer from at least one serious illness (Adhikari et al.,  2009 ). The chances of premature death rise with the number of cigarettes consumed. At the same time, the benefits of quitting include return of most disease risks to nonsmoker levels within one to ten years. In a study of 1.2 million British women, those who had been regular smokers but stopped before they reached age 45 avoided 90 percent of the elevated risk of premature death from cigarettes (Pirie et al.,  2012 ). And those who quit before age 35 avoided 97 percent of the added risk.

Nearly 70 percent of U.S. smokers say they want to quit completely, but less than half who saw their doctors in the past year received advice to do so (Centers for Disease Control and Prevention, 2012e). Although millions have stopped without help, those who use cessation aids (for example, nicotine gum, nasal spray, or patches, designed to reduce dependency gradually) or enter treatment programs often fail: As many as 90 percent start smoking again within six months (Aveyard & Raw,  2012 ). Unfortunately, too few treatments last long enough, effectively combine counseling with medications that reduce nicotine withdrawal symptoms, and teach skills for avoiding relapse.


National surveys reveal that about 10 percent of men and 3 percent of women in the United States are heavy drinkers (U.S. Department of Health and Human Services,  2011e ). About one-third of them are alcoholics—people who cannot limit their alcohol use. In men, alcoholism usually begins in the teens and early twenties and worsens over the following decade. In women, its onset is typically later, in the twenties and thirties, and its course is more variable. Many alcoholics are also addicted to other substances, including nicotine and illegal mood-altering drugs.

Twin and adoption studies support a genetic contribution to alcoholism. Genes moderating alcohol metabolism and those influencing impulsivity and sensation seeking (temperamental traits linked to alcohol addiction) are involved (Buscemi & Turchi,  2011 ). But whether a person comes to deal with life’s problems through drinking is greatly affected by environment: Half of alcoholics have no family history of problem drinking. Alcoholism crosses SES and ethnic lines but is higher in some groups than others (Schuckit,  2009 ). In cultures where alcohol is a traditional part of religious or ceremonial activities, people are less likely to abuse it. Where access to alcohol is carefully controlled and viewed as a sign of adulthood, dependency is more likely—factors that may, in part, explain why college students drink more heavily than young people not enrolled in college (Slutske et al.,  2004 ). Poverty, hopelessness, and a history of physical or sexual abuse in childhood are among factors that sharply increase the risk of excessive drinking (Donatelle,  2012 ; Lown et al.,  2011 ; U.S. Department of Health and Human Services,  2011e ).


In cultures where alcohol is a traditional part of religious or ceremonial activities, people are less likely to abuse it. For Jewish families, holiday celebrations, such as this Passover Seder, include blessing and drinking wine.

Alcohol acts as a depressant, impairing the brain’s ability to control thought and action. In a heavy drinker, it relieves anxiety at first but then induces it as the effects wear off, so the alcoholic drinks again. Chronic alcohol use does widespread physical damage. Its best-known complication is liver disease, but it is also linked to cardiovascular disease, inflammation of the pancreas, irritation of the intestinal tract, bone marrow problems, disorders of the blood and joints, and some forms of cancer. Over time, alcohol causes brain damage, leading to confusion, apathy, inability to learn, and impaired memory (O’Connor,  2012 ). The costs to society are enormous. About 30 percent of fatal motor vehicle crashes in the United States involve drivers who have been drinking (U.S. Department of Transportation,  2012 ). Nearly half of convicted felons are alcoholics, and about half of police activities in large cities involve alcohol-related offenses (McKim & Hancock,  2013 ). Alcohol frequently plays a part in sexual coercion, including date rape, and in domestic violence.

The most successful treatments combine personal and family counseling, group support, and aversion therapy (use of medication that produces a physically unpleasant reaction to alcohol, such as nausea and vomiting). Alcoholics Anonymous, a community support approach, helps many people exert greater control over their lives through the encouragement of others with similar problems. Nevertheless, breaking an addiction that has dominated a person’s life is difficult; about 50 percent of alcoholics relapse within a few months (Kirshenbaum, Olsen, & Bickel,  2009 ).


At the end of high school, about 65 percent of U.S. young people have had sexual intercourse; by age 25, nearly all have done so, and the gender and SES differences that were apparent in adolescence (see  page 374  in  Chapter 11 ) have diminished (U.S. Department of Health and Human Services,  2012d ). Compared with earlier generations, contemporary adults display a wider range of sexual choices and lifestyles, including cohabitation, marriage, extramarital experiences, and orientation toward a heterosexual or homosexual partner. In this chapter, we explore the attitudes, behaviors, and health concerns that arise as sexual activity becomes a regular event in young people’s lives. In  Chapter 14 , we focus on the emotional side of close relationships.

Heterosexual Attitudes and Behavior.

One Friday evening, Sharese accompanied her roommate Heather to a young singles bar, where two young men soon joined them. Faithful to her boyfriend, Ernie, whom she had met in college and who worked in another city, Sharese remained aloof for the next hour. In contrast, Heather was talkative and gave one of the men, Rich, her phone number. The next weekend, Heather went out with Rich. On the second date, they had intercourse, but the romance lasted only a few weeks. Aware of Heather’s more adventurous sex life, Sharese wondered whether her own was normal. Only after several months of dating exclusively had she and Ernie slept together.

Since the 1950s, public display of sexuality in movies, newspapers, magazines, and books has steadily increased, fostering the impression that Americans are more sexually active than ever before. What are contemporary adults’ sexual attitudes and behaviors really like? Answers were difficult to find until the National Health and Social Life Survey, the first in-depth study of U.S. adults’ sex lives based on a nationally representative sample, was carried out in the early 1990s. Nearly four out of five randomly chosen 18- to 59-year-olds agreed to participate—3,400 in all. Findings were remarkably similar to those of surveys conducted at about the same time in France, Great Britain, and Finland, and to a more recent U.S. survey (Langer,  2004 ; Laumann et al.,  1994 ; Michael et al.,  1994 ).

Recall from  Chapter 11  that the sex lives of most teenagers do not dovetail with exciting media images. The same is true of adults in Western nations. Although their sexual practices are diverse, they are far less sexually active than we have come to believe. Monogamous, emotionally committed couples like Sharese and Ernie are more typical (and more satisfied) than couples like Heather and Rich.

Sexual partners, whether dating, cohabiting, or married, tend to be similar in age (within five years), education, ethnicity, and (to a lesser extent) religion. In addition, people who establish lasting relationships often meet in conventional ways—through friends or family members, or at school or social events where people similar to themselves congregate. The powerful influence of social networks on sexual choice is adaptive. Sustaining an intimate relationship is easier when adults share interests and values and people they know approve of the match.

Over the past decade, the Internet has become an increasingly popular way to initiate relationships: More than one-third of single adults go to dating websites or other online venues in search of romantic partners. In a survey of a nationally representative sample of 4,000 Americans, most of whom were married or in a romantic relationship, 22 percent said they had met on the Internet, making it the second most common way to meet a partner, just behind meeting through friends (Finkel et al.,  2012 ). In fact, knowing someone who has successfully engaged in Internet dating strongly predicts single adults’ willingness to look for a partner on dating websites (Sautter, Tippett, & Morgan,  2010 ; Sprecher,  2011 ). As reports of dating success spread through social networks, use of Internet dating services is likely to increase further.


The Internet is an increasingly popular way to initiate romantic relationships. Here, young people attend a “speed dating”event, organized online, where they have brief conversations with potential partners.

Nevertheless, the services of online dating sites sometimes undermine, rather than enhance, the chances of forming a successful romantic relationship. Relying on Internet dating profiles and computer-mediated communication omits aspects of direct social interaction that are vital for assessing one’s compatibility with a potential partner. Especially when computer-mediated communication persists for a long time (six weeks or more), people form idealized impressions that often lead to disappointment at face-to-face meetings (Finkel et al.,  2012 ; Ramirez & Zhang,  2007 ). Furthermore, having a large pool of potential partners from which to choose can promote a persistent “shopping mentality,”which reduces online daters’ willingness to make a commitment (Heino, Ellison, & Gibbs,  2010 ). Finally, the techniques that matching sites claim to use to pair partners—sophisticated analyses of information daters provide—have not demonstrated any greater success than conventional off-line means of introducing people.

Consistent with popular belief, Americans today have more sexual partners over their lifetimes than they did a generation ago. For example, one-third of adults over age 50 have had five or more partners, whereas half of 30- to 50-year-olds have accumulated that many in much less time. And although women are more opposed to casual sex then men, after excluding a small number of men (less than 3 percent) with a great many sexual partners, contemporary men and women differ little in average number of lifetime sexual partners (Langer,  2004 ). Why is this so? From an evolutionary perspective, contemporary effective contraception has permitted sexual activity with little risk of pregnancy, enabling women to have as many partners as men without risking the welfare of their offspring.

But when adults of any age are asked how many partners they have had in the past year, the usual reply (for about 70 percent) is one. What explains the trend toward more relationships in the context of sexual commitment? In the past, dating several partners was followed by marriage. Today, dating more often gives way to cohabitation, which leads either to marriage or to breakup. In addition, people are marrying later, and the divorce rate remains high. Together, these factors create more opportunities for new partners. Still, survey evidence indicates that most U.S. 18- to 29-year-olds want to settle down eventually with a mutually exclusive lifetime sexual partner (Arnett,  2012 ). In line with this goal, most people spend the majority of their lives with one partner.

How often do Americans have sex? Not nearly as frequently as the media would suggest. One-third of 18- to 59-year-olds have intercourse as often as twice a week, another third have it a few times a month, and the remaining third have it a few times a year or not at all. Three factors affect frequency of sexual activity: age, whether people are cohabiting or married, and how long the couple has been together. Single people have more partners, but this does not translate into more sex! Sexual activity increases through the twenties and (for men) the thirties as people either cohabit or marry. Then it declines, even though hormone levels have not changed much (Herbenick et al.,  2010 ; Langer,  2004 ). The demands of daily life—working, commuting, taking care of home and children—are probably responsible. Despite the common assumption that sexual practices vary greatly across social groups, the patterns just described are unaffected by education, SES, or ethnicity.

Most adults say they are happy with their sex lives. For those in committed relationships, more than 80 percent report feeling “extremely physically and emotionally satisfied,”a figure that rises to 88 percent for married couples. In contrast, as number of sex partners increases, satisfaction declines sharply. These findings challenge two stereotypes—that marriage is sexually dull and that people who engage in casual dating have the “hottest”sex (Paik,  2010 ). In actuality, individuals prone to unsatisfying relationships are more likely to prefer “hookups”or “friends with benefits.”

A minority of U.S. adults—women more often than men—report persistent sexual problems. For women, the two most frequent difficulties are lack of interest in sex (39 percent) and inability to achieve orgasm (20 percent) (Shifren et al.,  2008 ). Most often mentioned by men are climaxing too early (29 percent) and anxiety about performance (16 percent). Sexual difficulties are linked to low SES and psychological stress and are more common among people who are not married, have had more than five partners, and have experienced sexual abuse during childhood or (for women) sexual coercion in adulthood (Laumann, Paik, & Rosen,  1999 ). As these findings suggest, a history of unfavorable relationships and sexual experiences increases the risk of sexual dysfunction.

But overall, a completely untroubled physical experience is not essential for sexual happiness. Surveys of adults repeatedly show that satisfying sex involves more than technique; it is attained in the context of love, affection, and fidelity (Bancroft,  2002 ; Santtila et al.,  2008 ). In sum, happiness with partnered sex is linked to an emotionally fulfilling relationship, good mental health, and overall contentment with life.

Homosexual Attitudes and Behavior.

The majority of Americans support civil liberties and equal employment opportunities for gay men, lesbians, and bisexuals. And attitudes toward sex and romantic relationships between adults of the same sex have gradually become more accepting: Nearly half of U.S. adults say same-sex sexual relations are “not wrong at all”or only “sometimes wrong”and support same-sex marriage, and three-fourths favor same-sex civil unions (Pew Research Center,  2013 ; Smith, 2011b).

Homosexuals’ political activism and greater openness about their sexual orientation have contributed to gains in acceptance. Exposure and interpersonal contact reduce negative attitudes. But perhaps because they are especially concerned with gender-role conformity, heterosexual men judge homosexuals (and especially gay men) more harshly than do heterosexual women (Herek,  2009 ). Also, the United States lags behind Western Europe in positive attitudes. Nations with greatest acceptance tend to have a greater proportion of highly educated, economically well-off citizens who are low in religiosity (Smith,  2011a ).

An estimated 3.5 percent of U.S. men and women—more than 8 million adults—identify as lesbian, gay, or bisexual, with women substantially more likely than men to report a bisexual orientation. Estimates from national surveys conducted in Australia, Canada, and Western Europe tend to be lower, at 1.5 to 2 percent (Gates,  2011 ). But many people who are gay, lesbian, or bisexual do not report themselves as such in survey research. This unwillingness to answer questions, engendered by a climate of persecution, has limited researchers’ access to information about the sex lives of gay men and lesbians. The little evidence available indicates that homosexual sex follows many of the same rules as heterosexual sex: People tend to seek out partners similar in education and background to themselves; partners in committed relationships have sex more often and are more satisfied; and the overall frequency of sex is modest (Laumann et al.,  1994 ; Michael et al.,  1994 ).

Homosexuals tend to live in or near large cities, where many others share their sexual orientation, or in college towns, where attitudes are more accepting. Living in small communities where prejudice is intense and no social network exists through which to find compatible homosexual partners is isolating, lonely, and predictive of mental health problems (Meyer,  2003 ).

People who identify themselves as gay or lesbian also tend to be well-educated (Mercer et al.,  2007 ). In the National Health and Social Life Survey, twice as many college-educated as high-school-educated men and eight times as many college-educated as high-school-educated women reported a same-sex orientation. Although the reasons for these findings are not clear, they probably reflect greater social and sexual liberalism among the more highly educated and therefore greater willingness to disclose homosexuality.

Sexually Transmitted Diseases.

In the United States, one in every four individuals is likely to contract a sexually transmitted disease (STD) at some point in life (U.S. Department of Health and Human Services,  2011b ). Although the incidence is highest in adolescence, STDs continue to be prevalent in early adulthood. During the teens and twenties, people accumulate most of their sexual partners, and they often do not take appropriate precautions to prevent the spread of STDs (see  page 377  in  Chapter 11 ). The overall rate of STDs is higher among women than men because it is at least twice as easy for a man to infect a woman with any STD, including AIDS, than for a woman to infect a man.

Although AIDS, the most deadly STD, remains concentrated among gay men and intravenous drug abusers, many homosexuals have responded to its spread by changing their sexual practices—limiting number of sexual partners, choosing partners more carefully, and using latex condoms consistently and correctly. Heterosexuals at high risk due to a history of many partners have done the same. Still, the annual number of U.S. new HIV infections—about 48,000—has remained stable since the late 1990s, and AIDS remains the sixth-leading cause of death among U.S. young adults (refer to  Figure 13.4  on  page 438 ). The incidence of HIV-positive adults is higher in the United States than in any other industrialized nation (OECD,  2012b ). The disease is spreading most rapidly through men having sex with men and through heterosexual contact in poverty-stricken minority groups, among whom high rates of intravenous drug abuse coexist with poor health, inadequate education, high life stress, and hopelessness (Centers for Disease Control and Prevention,  2012c ). People overwhelmed by these problems are least likely to take preventive measures.


Gay and lesbian romantic partners, like heterosexual partners, tend to be similar in education and background. With greater openness and political activism, attitudes toward same-sex relationships have become more accepting.

Yet AIDS can be contained and reduced—through sex education extending from childhood into adulthood and through access to health services, condoms, and clean needles and syringes for high-risk individuals. In view of the rise in AIDS among women, who currently account for one-fourth of cases in North America and Western Europe and more than half in developing countries, a special need exists for female-controlled preventive measures. Drug-based vaginal gels that kill or inactivate the virus have shown promising results and are undergoing further testing.

Sexual Coercion.

After a long day of classes, Sharese flipped on the TV and caught a talk show on sex without consent. Karen, a 25-year-old woman, described her husband Mike pushing, slapping, verbally insulting, and forcing her to have sex. “It was a control thing,”Karen explained tearfully. “He complained that I wouldn’t always do what he wanted. I was confused and blamed myself. I didn’t leave because I was sure he’d come after me and get more violent.”

One day, as Karen was speaking long distance to her mother on the phone, Mike grabbed the receiver and shouted, “She’s not the woman I married! I’ll kill her if she doesn’t shape up!”Alarmed, Karen’s parents arrived by plane the next day to rescue her and helped her start divorce proceedings and get treatment.

An estimated 18 percent of U.S. women, sometime in their lives, have endured rape, legally defined as intercourse by force, by threat of harm, or when the victim is incapable of giving consent (because of mental illness, mental retardation, or alcohol consumption). About 45 percent of women have experienced other forms of sexual aggression. The majority of victims (eight out of ten) are under age 30 (Black et al.,  2011 ; Schewe,  2007 ). Women are vulnerable to partners, acquaintances, and strangers, but in most instances their abusers are men they know well. Sexual coercion crosses SES and ethnic lines; people of all walks of life are offenders and victims.

Personal characteristics of the man with whom a woman is involved are far better predictors of her chances of becoming a victim than her own characteristics. Men who engage in sexual assault tend to be manipulative of others, lack empathy and remorse, pursue casual sexual relationships rather than emotional intimacy, approve of violence against women, and accept rape myths (such as “Women really want to be raped”). Perpetrators also tend to interpret women’s social behaviors inaccurately, viewing friendliness as seductiveness, assertiveness as hostility, and resistance as desire (Abbey & Jacques-Tiura,  2011 ; Abbey & McAuslan,  2004 ). Furthermore, sexual abuse in childhood, promiscuity in adolescence, and alcohol abuse in adulthood are associated with sexual coercion. Approximately half of all sexual assaults take place while people are intoxicated (Black et al.,  2011 ).


Obtain from your campus student services or police department the number of sexual assaults reported by students during the most recent year. What percentage involved alcohol? What prevention and intervention services does your college offer?

Cultural forces also contribute. When men are taught from an early age to be dominant, competitive, and aggressive and women to be submissive and cooperative, the themes of rape are reinforced. Societal acceptance of violence also sets the stage for rape, which typically occurs in relationships in which other forms of aggression are commonplace. Exposure to sexually aggressive pornography and other media images, which portray women desiring and enjoying the assault, also promote sexual coercion by dulling sensitivity to its harmful consequences.

About 7 percent of men have been victims of coercive sexual behavior. Although rape victims report mostly male perpetrators, women are largely responsible for other forms of sexual coercion against men (Black et al,  2011 ). Victimized men often say that women who committed these acts used threats of physical force or actual force, encouraged them to get drunk, or threatened to end the relationship unless they complied (Anderson & Savage,  2005 ). Unfortunately, authorities rarely recognize female-initiated forced sex as illegal, and few men report these crimes.


Women’s and men’s psychological reactions to rape resemble those of survivors of extreme trauma. Immediate responses—shock, confusion, withdrawal, and psychological numbing—eventually give way to chronic fatigue, tension, disturbed sleep, depression, substance abuse, social anxiety, and suicidal thoughts (Black et al.,  2011 ; Schewe,  2007 ). Victims of ongoing sexual coercion may fall into a pattern of extreme passivity and fear of taking any action.

One-third to one-half of female rape victims are physically injured. From 4 to 30 percent contract sexually transmitted diseases, and pregnancy results in about 5 percent of cases. Furthermore, victims of rape (and other sexual crimes) report more symptoms of illness across almost all body systems. And they are more likely to engage in negative health behaviors, including smoking and alcohol use (McFarlane et al.,  2005 ; Schewe,  2007 ).


In 2012, in New Delhi, India, the brutal gang rape of a 23-year-old student, who died a month later from her injuries, prompted candlelight vigils and other protests throughout the country. Participants demanded increased government and police action to prevent sexual violence against women.

Applying What We Know Preventing Sexual Coercion

Strategy Explanation
Reduce gender stereotyping and gender inequalities. The roots of men’s sexual coercion of women lie in the historically subordinate status of women. Unequal educational and employment opportunities keep women economically dependent on men and therefore poorly equipped to avoid partner violence. At the same time, increased public awareness that women sometimes commit sexually aggressive acts is needed.
Mandate treatment for men and women who physically or sexually assault their partners. Ingredients of effective intervention include combating rape myths and inducing personal responsibility for violent behavior; teaching social awareness, social skills, and anger management; and developing a support system to prevent future attacks.
Expand interventions for children and adolescents who have witnessed violence between their parents. Although most child witnesses to parental violence do not become involved in abusive relationships as adults, they are at increased risk.
Teach both men and women to take precautions that lower the risk of sexual assault. Risk of sexual assault can be reduced by communicating sexual limits clearl

Place this order or similar order and get an amazing discount. USE Discount code “GET20” for 20% discount