Puberty

Puberty refers to the years of rapid physical growth and sexual maturation that end childhood, producing a person of adult size, shape, and sexuality. The forces of puberty are unleashed by a cascade of hormones that produce external growth and internal changes, including heightened emotions and sexual desires.

Average Ages and Changes

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The process of puberty normally starts sometime between ages 8 and 14, and most physical changes are complete within four years—although some height, weight, and reproductive increases may occur for several more years. Over the past decades the age of puberty has declined, perhaps for both sexes, although the evidence is more solid for girls (Biro et al., 2013; Herman-Giddens, 2013).

Video: The Timing of Puberty

menarche

A girl’s first menstrual period, signalling that she has begun ovulation. Pregnancy is biologically possible, but ovulation and menstruation are often irregular for years after menarche.

For girls, the observable changes of puberty usually begin with nipple growth. Soon a few pubic hairs are visible, followed by a peak growth spurt, widening of the hips, menarche (the first menstrual period), full pubic-hair pattern, and breast maturation (Susman et al., 2010). The average age of menarche among normal-weight girls is about 12 years, 4 months (Biro et al., 2013).

spermarche

A boy’s first ejaculation of sperm. Erections can occur as early as infancy, but ejaculation signals sperm production. Spermarche may occur during sleep (in a “wet dream”) or via direct stimulation.

For boys, the usual sequence is growth of the testes, initial pubic-hair growth, growth of the penis, spermarche (first ejaculation of seminal fluid), first facial hair, peak growth, deepening of the voice, and final pubic-hair and beard pattern (Biro et al., 2001; Herman-Giddens et al., 2012; Susman et al., 2010). The typical age of spermarche is just under 13 years. Age varies markedly within and between nations: These are averages in the United States.

pituitary

A gland in the brain that produces many hormones, including those that regulate growth and that signal the adrenal and sex glands to produce additional hormones.

adrenal glands

Two glands, located above the kidneys, that produce hormones in response to signals from the pituitary.

HORMONES Puberty begins before those observable changes with an invisible event—a marked increase in hormones, which are body chemicals that regulate hunger, sleep, moods, stress, sexual desire, immunity, reproduction, and many other biological processes. The pituitary, deep within the brain, signals the hypothalamus, another brain structure, that puberty should begin. First to receive the signal are the adrenal glands, located above the kidneys at either side of the lower back.

Table 9.1: At About This Time: The Sequence of Puberty
Girls Approximate Average Age* Boys
Ovaries increase production of estrogen and progesterone** 9
Uterus and vagina begin to grow larger Testes increase production of testosterone**
Breast “bud” stage 10 Testes and scrotum grow larger
Pubic hair begins to appear; weight spurt begins 11
Peak height spurt 11½ Pubic hair begins to appear
Peak muscle and organ growth; hips become noticeably wider 12 Penis growth begins
Menarche (first menstrual period) 12½ Spermarche (first ejaculation); weight spurt begins
First ovulation 13 Peak height spurt
Voice lowers 14 Peak muscle and organ growth; shoulders become noticeably broader
Final pubic-hair pattern 15 Voice lowers; visible facial hair
Full breast growth 16
18 Final pubic-hair pattern
*Average ages are rough approximations, with many perfectly normal, healthy adolescents as much as three years behind these ages.
**Estrogen and testosterone influence sexual characteristics, including reproduction. Charted here are the increases produced by the gonads (sex glands). The ovaries produce estrogens and the testes produce androgens, especially testosterone. Adrenal glands produce some of both kinds of hormones (not shown).

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Do They See Beauty? Both young women—the Mexican 15-year-old preparing for her Quinceañera and the Malaysian teen applying a rice facial mask—look wistful, even worried. They are typical of teenage girls everywhere, who do not realize how lovely they are.

gonads

The sex glands (ovaries in females, testicles in males). The gonads produce hormones and gametes.

estradiol

A sex hormone, considered to be the chief estrogen (female hormone). Females produce much more estradiol than males do.

testosterone

A sex hormone, the best known of the androgens (male hormones); secreted in far greater amounts by males than by females.

The pituitary also activates the gonads, or sex glands (ovaries in females; testes, or testicles, in males). One hormone in particular, GnRH (gonadotropin-releasing hormone), causes the gonads to enlarge and dramatically increase their production of sex hormones, chiefly estradiol in girls and testosterone in boys.

Estrogens (including estradiol) are female hormones and androgens (including testosterone) are male hormones, although both sexes have some of both. The ovaries produce high levels of estrogens and the testes produce dramatic increases in androgens. This “surge of hormones” affects bodies, brains, and behavior before any visible signs of puberty appear, “well before the teens” (Peper & Dahl, 2013, p. 134).

The activated gonads begin to release ova (at menarche) or sperm (at spermarche). Conception is possible, although peak fertility occurs four to six years later. Hormones also awaken interest in sex, as young teenagers fantasize—at first about people who are unlikely to reciprocate (celebrities, teachers) and then about their peers nearby.

Hormones may underlie differences in psychopathology. Compared to the other sex, adolescent males are almost twice as likely to develop schizophrenia and adolescent females more than twice as likely to develop major depression. Of course, hormones are never the sole cause of psychopathology (Tackett et al., 2014; Rudolph, 2014).

Remember that body, brain, and behavior always interact. Sexual thoughts themselves can cause physiological and neurological processes, not just result from them. Cortisol (another hormone) levels rise at puberty, and that makes adolescents quicker to become angry or upset (Goddings et al., 2012; Klein & Romeo, 2013).

THINK CRITICALLY: If a child seems to be unusually short, or unusually slow in reaching puberty, would you give the child hormones? Why or why not?

Then emotions, in turn, increase hormones. For example, when other people react to emerging breasts or beards, that evokes thoughts and frustrations in the adolescent, which raises hormone levels, propels physiological development, and triggers more emotions. Thus the internal and external changes each affect the other.

circadian rhythm

A day–night cycle of biological activity that occurs approximately every 24 hours (circadian means “about a day”).

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I Covered That Teachers everywhere complain that students don’t remember what they were taught. Maybe schedules, not daydreaming, are to blame.

BODY RHYTHMS The brain of every living creature responds to the environment with natural rhythms that rise and fall by the day and season. For example, in children, height increases more rapidly in summer and weight in winter. Many rhythms are circadian, which means they are on a daily cycle. That is why well-rested people tend to wake up at the same time on weekends as during the week, and they also get sleepy at the same time each night.

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In addition, some individuals (especially males) are more alert in the evening than in the morning. Other people are the opposite, filled with energy in the morning and then fading as the day wears on. Those differences are genetic.

In addition, at puberty, hormones cause a phase delay in the circadian sleep–wake cycles. That compels many teens to be wide awake and hungry at midnight but half asleep, with neither appetite nor energy, all morning. For teens who are already evening people, the phase delay increases the risk of problems: They are up when adults are asleep, but adults still make them get out of bed at dawn. Consequently, in many nations, sleep deprivation increases during adolescence (see Figure 9.1) (Roenneberg et al., 2012).

Question 9.1

OBSERVATION QUIZ

As you see, the problems may be worse for girls. Why is that?

Girls tend to spend more time studying, talking to friends, and getting ready in the morning. Other data show that many girls get less than seven hours of sleep per night.

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Figure 9.1: FIGURE 9.1 Sleepyheads Three of every four high school seniors are sleep deprived. Even if they go to sleep at midnight, as many do, they must get up before 8 A.M., as almost all do. Then they are tired all day.

To make it worse, “the blue spectrum light from TV, computer, and personal-device screens may have particularly strong effects on the human circadian system” (Peper & Dahl, 2013, p. 137). Watching late-night TV, working on the computer, or texting friends at 10 P.M. interferes with normal nighttime sleepiness. Sleeping late on weekends is a sign of deprivation, not compensation.

Sleep deprivation and irregular sleep schedules increase the risk of insomnia, nightmares, mood disorders (depression, conduct disorder, anxiety), and falling asleep while driving. In addition, sleepy people don’t learn as well as they do when rested. Many adults ignore these facts, as the following explains.

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OPPOSING PERSPECTIVES

Algebra at 7 A.M.? Get Real!

Adults sometimes fight against what is natural to adolescents. This is evident with sexual curiosity (“you’re too young to think about boys”) and circadian rhythm (“go to sleep, you need to get up for school”).

Many adults think adolescents belong at home, just when many adolescents much prefer to be with friends. In 2014, Baltimore implemented a law that required young adolescents (under age 14) to be home by 9 P.M. and older ones (14- to 16-year-olds) off the streets by 10 P.M. on school nights and 11 P.M. on weekends. The idea is that adolescents should be sound asleep in their own beds before midnight.

For many adolescent bodies, early sleep and then early rising are almost impossible. As a result, many sleep-deprived teenagers nod off in class (see Figure 9.2) and take drugs (from caffeine to speed) to stay awake (Mueller et al., 2011; Patrick & Schulenberg, 2011).

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Figure 9.2: FIGURE 9.2 Dreaming and Learning? This graph shows the percentage of U.S. students who, once a week or more, fall asleep in class or are too tired to exercise. Not shown are those who say they are usually tired (59 percent of high school students) or who doze in class “almost every day” (8 percent).

Data on the circadian rhythm and the teenage brain convinced social scientists at the University of Minnesota to ask 17 school districts to start high school later. Parents disagreed. Many (42 percent) thought high school should begin before 8:00 A.M. Some (20 percent) wanted their teenagers out of the house by 7:15 A.M. (Wahlstrom, 2002).

Other adults had their own reasons for wanting high school to begin early. Teachers thought that learning was more efficient in the morning; bus drivers hated rush hour; cafeteria workers liked to go home in mid-afternoon; police wanted teenagers off the streets before dusk; coaches needed after-school sports events to end before dark; business owners hired teens for the early evening shift; community groups wanted the school gyms available in the late afternoon.

Initially only one Minnesota school district (Edina) changed the schedule of their high school day, from 7:25–2:05 to 8:30–3:10. After a trial year, most parents (93 percent) and virtually all students approved. One student said, “I have only fallen asleep in school once this whole year, and last year I fell asleep about three times a week” (quoted in Wahlstrom, 2002, p. 190). Fewer students were absent, late, disruptive, or sick (the school nurse became an advocate). Grades rose.

Other school districts noticed. Minneapolis high schools changed their start time from 7:15 to 8:40. Attendance and graduation rates improved. School boards in South Burlington (Vermont), West Des Moines (Iowa), Tulsa (Oklahoma), Arlington (Virginia), Palo Alto (California), and Milwaukee (Wisconsin) voted to start high school later, from an average of 7:45 to an average of 8:30 (Tonn, 2006; Snider, 2012). Unexpected advantages appeared: more efficient energy use, less adolescent depression, and in Tulsa, unprecedented athletic championships.

Many school districts remain stuck to traditional schedules, scheduling school buses to drop off teenagers and then pick up the younger children. Although “the science is there; the will to change is not” (Snider, 2012).

One example comes from Fairfax County (Virginia) where two opposing groups—SLEEP (Start Later for Excellence in Education Proposal) versus WAKE (Worried About Keeping Extra-Curriculars)—argued. One sports reporter wrote:

The later start would hinder teams without lighted practice fields. Hinder kids who work after-school jobs to save for college or to help support their families. Hinder teachers who work second jobs or take late-afternoon college classes. Hinder commuters who would get stopped behind more buses during peak traffic times. Hinder kids who might otherwise seek after-school academic help, or club or team affiliation. Hinder families that depend on high school children to watch younger siblings after school. Hinder community groups that use school and park facilities in the late afternoons and evenings.

[Williams, 2009]

Note that Williams never argued that learning would be reduced, because that would be untrue. He wrote that science was on the side of change but reality was not. To developmentalists, of course, science is reality.

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In 2009, the Fairfax school board voted to keep the high school start at 7:20 A.M. The SLEEP advocates kept trying. On the eighth try, the Fairfax school board in 2012 finally set a goal: High schools should not start before 8:00 A.M. They hired a team to figure out how to implement that goal. As of 2014, they had not done so.

There is a new reason to change. In August 2014, the American Academy of Pediatrics concluded that high school should not begin until 8:30 or 9:00 A.M., because adolescent sleep deprivation causes intellectual and behavioral problems. They noted that 43 percent of high schools in the United States start before 8:00 A.M. The clash between tradition and science, or between adult expectations and adolescent bodies, continues.

Many Reasons for Variations

That six-year range in onset of puberty (age 8 to 14) is troubling for parents and preteens who want to be ready but not premature. More precise prediction is possible.

GENES AND GENDER About two-thirds of the variation in age of puberty is genetic, evident not only in families but also in ethnic groups (Dvornyk & Waqar-ul-Haq, 2012; Biro et al., 2013). African Americans reach puberty, on average, about seven months earlier than European or Hispanic Americans; Chinese Americans average several months later.

The other major influence on age of puberty comes from the sex chromosomes. In height, the average girl is two years ahead of the average boy: The female height spurt occurs before menarche, whereas for boys the increase in height is relatively late, after spermarche. Thus, a sixth-grade boy with sexual fantasies about the taller girls in his class is neither perverted nor precocious; his hormones are simply ahead of his height.

FAT Body fat also affects age of puberty. Heavy girls reach menarche years earlier than malnourished ones do. Most girls weigh at least 100 pounds (45 kilograms) before menarche (Berkey et al., 2000). Although severe malnutrition always delays puberty, body fat may not be as necessary for boys. Indeed, obese boys are often delayed in puberty compared to boys who are neither slim nor overweight (Tackett et al., 2014).

Malnutrition causes many youths to reach puberty at age 15 or later in parts of Africa, whereas their genetic relatives in North America mature much earlier. Similarly, malnutrition is the main reason puberty began at about age 17 in sixteenth-century Europe.

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Brothers, but Not Twins These brothers are close in age and both exhibit the emotional excitement that accompanies the hormones of puberty. The past year has led to many rapid physical changes, especially for the older boy.

secular trend

Advances in growth and maturation that result from modern nutrition. For example, improved nutrition and medical care over the past 200 years has led to earlier puberty and taller average height.

Since then, puberty has occurred at younger and younger ages (an example of what is called the secular trend, the increases in human growth as nutrition improved). More food availability led to weight gain in childhood, and that has led to earlier puberty for girls and taller average height for both sexes (Floud et al., 2011; Fogel & Grotte, 2011).

One curious bit of evidence of the secular trend is that U.S. presidents have gotten taller. James Madison, the fourth president, was shortest at 5 feet, 4 inches; Barack Obama is 6 feet, 1 inch tall.

The secular trend seems to have stopped in developed nations, because adequate nutrition allows everyone to reach their genetic potential. Currently, fewer young men look down at their short fathers, or girls at their little mothers, unless their parents were born in Asia or Africa, where the secular trend is still evident.

There is one possible exception in developed nations to the statement “the secular trend has stopped.” Very early puberty, before age 8 (called precocious puberty), may be increasing, especially in girls, although it is still rare (perhaps 2 percent) (Sørensen et al., 2012). Sometimes precocious puberty is genetic (perhaps 20 percent), but the cause of the increase is largely unknown—perhaps childhood obesity or new chemicals in the environment.

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Some research finds that puberty is delayed, not accelerated, in boys who were exposed prenatally to phthalates and bisphenol A (K. Ferguson et al., 2014), or who experienced heavy doses of pesticides in boyhood (T. Lam et al., 2014). Phthalates may delay puberty in girls as well (Wolff et al., 2014).

Caution is needed here. No doubt, heavy doses of many chemicals and pesticides affect fish, frogs, insects, and birds, causing reproductive problems. However, as noted in Chapter 2, experts disagree about the impact on humans.

STRESS Stress hastens the hormonal onset of puberty, especially if a child’s parents are sick, drug-addicted, or divorced, or if the neighborhood is violent and impoverished. One study of sexually abused girls found that they began puberty seven months earlier, on average, than did a matched comparison group (Trickett et al., 2011). Particularly for girls who are genetically sensitive, puberty comes early if their family interaction causes high levels of cortisol but late if their family is supportive (Ellis et al., 2011; James et al., 2012).

The link between stress and puberty is one explanation for the fact that children born in one country and adopted in another tend to experience early puberty, especially if their first few years of life were in an institution or a chaotic home. An alternate explanation is that their age at adoption was underestimated, so puberty appears to occur early but actually is at the expected time (Hayes, 2013).

Why would cortisol trigger puberty? An answer comes from evolutionary theory. Thousands of years ago, if harsh conditions threatened survival of the species, adolescents needed to reproduce early and often to increase the chance that at least some children would reach adulthood. By contrast, in peaceful times, puberty could occur later, allowing children to postpone maturity and instead enjoy extra years of childhood nurturance from parents and grandparents.

Of course, this evolutionary rationale no longer applies. Today, early sexual activity and teen parenthood are more likely to harm communities than help the species. However, the genome has been shaped over millennia; if there is a puberty-starting allele that responds to social conditions, it still responds as it did thousands of years ago.

TOO EARLY, TOO LATE For most adolescents, these links between puberty, stress, and hormones are irrelevant. The only timing that matters is their friends’ schedules. No one wants to be too early or too late.

Question 9.2

OBSERVATION QUIZ

Who is least developed and who is most developed?

Impossible to be sure, but it seems as if the only one smiling is the least developed (note the size of her hands, the narrowness of her hips); the one on the left is the most developed (note hips, facial expression, height, and—most significant—her choice of clothes).

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All the Same? All four girls are 13, and all are from the same community in England. But as you see, each is on her own timetable, and that affects the clothes and expressions. Why is one in a tank top and shorts while another is in a heavy shirt and pants?

Think about the early-maturing girl. If she has visible breasts at age 10, the boys her age tease her; they are unnerved by the sexual creature in their midst. She must fit into a school chair designed for smaller children; she might hide her breasts in large T-shirts and bulky sweaters. Early-maturing girls tend to have lower self-esteem, more depression, and poorer body image than do other girls (Galvao et al., 2014; Compian et al., 2009).

Some early-maturing girls have older boyfriends, who are attracted to their womanly shape and girlish innocence. Having an older boyfriend bestows status, but it also increases problems (including drug and alcohol abuse) that arise from older teens (Mrug et al., 2014).

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The effects of early maturation on boys depend on context. In the United States, early-maturing boys who were born around 1930 often became leaders in high school and high wage earners as adults (Jones, 1965; Taga et al., 2006). Since about 1960, however, the risks associated with early male maturation have outweighed the benefits.

In the twenty-first century, early-maturing boys are more aggressive, law-breaking, and drug-abusing than the average boy (Biehl et al., 2007; Lynne et al., 2007; Mendle et al., 2012). This is not surprising: A boy who is experiencing rapid increases in testosterone, and whose body looks more like a man than a child, is likely to cause trouble with parents, peers, schools, and the police.

Late puberty may also be difficult, especially for boys (Benoit et al., 2013). Slow-developing boys tend to be more anxious, depressed, and afraid of sex. Girls are less attracted to them, coaches less often want them on their teams, peers bully or tease them.

Becoming a Grown-Up

growth spurt

The relatively sudden and rapid physical growth that occurs during puberty. Each body part increases in size on a schedule: Weight usually precedes height, and growth of the limbs precedes growth of the torso.

Puberty causes two sets of changes. One set is marked by the growth spurt—a sudden, uneven jump in the size of almost every body part, turning children into adults. The other set is sexual; turning girls and boys into men and women who could become parents.

THE GROWTH SPURT Growth proceeds from the extremities to the core (the opposite of the earlier proximodistal growth). Thus, fingers and toes lengthen before hands and feet, hands and feet before arms and legs, arms and legs before the torso. This growth is not always symmetrical: One foot, one breast, or even one ear may grow later than the other.

Because the torso is the last body part to grow, many pubescent children are temporarily big-footed, long-legged, and short-waisted. If young teenagers complain that their jeans don’t fit, they are probably correct—even if those same jeans fit when their parents paid for them a month earlier. (Advance warning about rapid body growth occurs when parents first have to buy their children’s shoes in the adult section.)

As the growth spurt begins, children eat more and gain weight. Exactly when, where, and how much weight they gain depends on heredity, hormones, diet, exercise, and gender. By age 17, the average girl has twice the percentage of body fat as her male classmate, whose increased weight is mostly muscle.

A height spurt follows the weight spurt; then a year or two later a muscle spurt occurs. Thus, the pudginess and clumsiness of early puberty are usually gone by late adolescence. During these years, all the muscles increase in power.

Inner organs grow as well. Lungs triple in weight, allowing adolescents to breathe more deeply and slowly. The heart doubles in size as the heartbeat slows, decreasing the pulse rate while increasing blood pressure. Consequently, endurance improves: Some teenagers can run for miles or dance for hours. Fortunately, red blood cells increase in both sexes, dramatically more in boys, aiding oxygen transport during intense exercise.

One organ system, the lymphoid system (including tonsils and adenoids), decreases in size, so teenagers are less susceptible to respiratory ailments. As a result, mild asthma often switches off at puberty—half as many teenagers as children are asthmatic (MMWR, June 8, 2012), and teenagers have fewer colds and allergies than younger children.

When the larynx grows, the voice lowers, especially noticeable in boys. Another organ system, the skin, becomes oilier, sweatier, and more prone to acne. Hair also changes, becoming coarser and darker, with new hair under arms, on faces, and over sex organs. Specifics depend on genes as well as on hormones.

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Often teenagers cut, style, or grow their hair in ways their parents do not like, as a sign of independence. To become more attractive, many adolescents spend considerable time, money, and thought on their visible hair—growing, gelling, shaving, curling, straightening, highlighting, brushing, combing, styling, dyeing, wetting, and/or drying. In many ways, hair is far more than a growth characteristic; it is a display of sexuality.

primary sex characteristics

The parts of the body that are directly involved in reproduction, including the vagina, uterus, ovaries, testicles, and penis.

SEXUAL CHARACTERISTICS The body characteristics that are directly involved in conception and pregnancy are called primary sex characteristics. During puberty, every primary sex organ (the ovaries, uterus, penis, and testes) increases dramatically in size and matures in function. By the end of the process, reproduction is possible.

secondary sex characteristics

Physical traits that are not directly involved in reproduction but that indicate sexual maturity, such as a man’s beard and a woman’s breasts.

At the same time, development occurs in secondary sex characteristics. They do not directly affect reproduction (hence they are secondary) but signify gender.

One secondary characteristic is shape. Young boys and girls have similar shapes, but at puberty males widen at the shoulders and grow about 5 inches taller than females, while girls widen at the hips and develop breasts. Those curves are considered signs of womanhood, but neither breasts nor wide hips are required for conception; thus, they are secondary, not primary, sex characteristics.

Secondary sex characteristics are important psychologically, if not biologically. Breasts are an obvious example. Many adolescent girls buy “minimizer,” “maximizer,” “training,” or “shaping” bras, hoping that their breasts will conform to their idealized body image.

During the same years, many overweight boys are horrified to notice a swelling around their nipples—a temporary result of the erratic hormones of early puberty. If a boy’s breast growth is very disturbing, tamoxifen or plastic surgery can reduce the swelling, although many doctors prefer to let time deal with the problem (Morcos & Kizy, 2012).

Nutrition

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For the Audience Teenage eating behavior is influenced by other adolescents. Note the evident approval from the slightly older teenager, not from the younger boys. Would the eater have put his head back and mouth wide open if the only onlookers were his parents?

All the changes of puberty depend on adequate nourishment, yet many adolescents do not eat well. They often skip breakfast, binge at midnight, guzzle down unhealthy energy drinks, and munch on salty, processed snacks. Some eat so poorly that their health is damaged lifelong.

NUTRIENTS MISSING Family dinners correlate with healthy adolescent eating and well-being. However, this is tricky: If parents insist on family dinners, clashing directly with the teenager’s wish for independence, the benefits of such meals may be undercut by a sullen, angry diner (Meier & Musick, 2014).

Most adolescents consume enough calories, but in 2013 only 16 percent of high school seniors ate the recommended three or more servings of vegetables a day (MMWR, June 13, 2014). Deficiencies of iron, calcium, zinc, and other minerals are common.

Because menstruation depletes iron, anemia is more likely among adolescent girls than among people of any other age or sex. Boys may also be iron-deficient if they engage in physical labor or intensive sports: Muscles need iron for growth and strength.

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The cutoff for iron-deficiency anemia is higher for boys than girls because boys require more iron to be healthy (Morón & Viteri, 2009). Yet in developed as well as developing nations, adolescents tend to spurn iron-rich foods (beans, egg yolks, and lean meat) in favor of iron-poor chips, sweets, and fries.

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Diet Worldwide, adolescent obesity is increasing. Parental responses differ, from indifference to major concern. For some U.S. parents the response is to spend thousands of dollars trying to change their children, as is the case for the parents of these girls, eating breakfast at Wellspring, a California boarding school for overweight teenagers that costs $6,250 a month. Every day, these girls exercise more than 10,000 steps (tracked with a pedometer) and eat less than 20 grams of fat (normal is more than 60 grams).

Similarly, although the daily recommended intake of calcium for teenagers is 1,300 milligrams, the average U.S. teen consumes less than 500 milligrams a day. About half of adult bone mass is acquired from ages 10 to 20, which means many contemporary teenagers will eventually develop osteoporosis (fragile bones), a major cause of disability, injury, and death in late adulthood.

One reason for calcium deficiency is that milk drinking has declined. In 1961, most North American children drank at least 24 ounces (about three-fourths of a liter) of milk each day, providing most of their daily calcium requirement. Fifty years later, only 12.5 percent of high school students drank that much milk and 19 percent (more girls than boys) drank no milk at all (MMWR, June 13, 2014).

Fast-food establishments, serving tasty but not healthy food, cluster around high schools, with extra seating that encourages teenagers to hang out. This is especially true for high schools with large Hispanic populations, who are most at risk for obesity (Taber et al., 2011). Forty percent of Hispanic girls in U.S. high schools describe themselves as overweight, as do 27 percent of Hispanic boys (MMWR, June 13, 2014).

LaunchPad

Video Activity: Eating Disorders introduces the three main types of eating disorders and outlines the signs and symptoms of each.

body image

A person’s idea of how his or her body looks, especially related to size and shape.

BODY DISSATISFACTION One reason for poor nutrition among teenagers is anxiety about body image—that is, a person’s idea of how his or her body looks. Two-thirds of U.S. high school girls are trying to lose weight, even though only one-fourth are actually overweight or obese (MMWR, June 8, 2012).

Body image dissatisfaction occurs in adolescents of both sexes and every ethnic group, although each adolescent is troubled by particular characteristics that spring from their ancestral genes. Film stars and media models make this worse.

Many adolescents obsess about being too short or too tall, too wide in the hips or too narrow in the face, too hairy or not hairy enough, with fingers too long or legs too fat, and so on. Self-acceptance is difficult at every age, particularly when body changes are new. Indeed, adolescents may become depressed because of some characteristic they wish they had or did not have (Kuzucu et al., 2014).

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For a few, dissatisfaction with body image can be dangerous, even deadly. Eating disorders are rare in childhood but increase dramatically at puberty, accompanied by distorted body image, food obsession, and depression (Le Grange & Lock, 2011). Many teenagers, mostly girls, eat erratically or ingest drugs (especially diet pills) to lose weight; others, mostly boys, take steroids or creatine (Calzo et al., 2015) to increase muscle mass. Both may switch from obsessive dieting, to overeating, to overexercising, and back again.

Rates of obesity are falling in childhood but increasing in adolescence and adulthood in almost every nation, including the United States. In 2001, more than 15 percent of high school students were obese in only three states (Kentucky, Mississippi, and Tennessee). In 2013, 22 states had rates that high (MMWR, June 13, 2014).

EATING DISORDERS Obesity is an eating disorder at every age, and it is discussed in several other chapters of this book. Here we focus on three other eating disorders that appear in adolescence.

anorexia nervosa

An eating disorder characterized by self-starvation and obsession with weight. Affected individuals become pathologically thin, depriving their vital organs of nutrition.

Anorexia nervosa is characterized by voluntary starvation. It is the extreme of what many teenage girls think about their weight: They have a distorted body image, perceiving themselves as being too heavy. Those suffering from anorexia become very underweight, risking death by organ failure. Staying thin becomes an obsession.

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Not Just Dieting Elize, seen here sitting in a café in France, believes that she developed anorexia after she went on an extreme diet. Success with that diet led her to think that even less food would be better. She is recovering, but, as you see, she is still too thin.

Although anorexia existed earlier, it was not identified until about 1950, when some high-achieving, upper-class young women became so emaciated that they died. Soon anorexia was noticed among teenagers and young adults of every income, nation, and ethnicity.

The rate of anorexia spikes at puberty and again in emerging adulthood. Scientists disagree about the causes—genes, family influences, or culture—but in any case, sufferers and their families need life-saving help (Dring, 2015; Dodge & Simic, 2015).

bulimia nervosa

An eating disorder characterized by binge eating and subsequent purging, usually by induced vomiting and/or use of laxatives.

About three times as common as anorexia is bulimia nervosa (also called the binge–purge syndrome). A person overeats compulsively, devouring thousands of calories within an hour or two, and then purges through vomiting or laxatives, risking many health problems.

Binging and purging are common among adolescents. For instance, a 2013 survey found that within the previous month 6.6 percent of U.S. high school girls and 2.2 percent of boys vomited or took laxatives to lose weight, with marked variation by state—from 3.6 percent in Nebraska to 9 percent in Arizona (MMWR, June 13, 2014).

The third adolescent eating disorder is newly recognized in DSM-5: binge eating disorder. Some adolescents periodically and compulsively overeat, quickly consuming large amounts of ice cream, cake, or some other kind of food until their stomachs hurt. In binge eating disorder, overeating is done secretly, at least weekly for months. The sufferer does not purge (this is not bulimia) but feels out of control, distressed, and depressed.

All adolescents are vulnerable to unhealthy eating, because autonomy, anxiety, and body image can lead to disorders. Teenagers try new diets, go without food for 24 hours (as did 19 percent of U.S. high school girls in one typical month), or take diet drugs (6.6 percent) (MMWR, June 13, 2014). Parents are slow to recognize eating disorders, and they often delay in getting help (Thomson et al., 2014).

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THINK CRITICALLY: Rates of eating disorders in adolescence seem to be increasing. Should parents be blamed? Why or why not?

All eating disorders—obesity, anorexia, bulimia, and bingeing—have many causes, including cultural images, anxiety, depression, puberty, hormones, genes, childhood experiences, and current family pressures. Especially in adolescence, family function (not structure) is crucial in treatment (Tetzlaff & Hilbert, 2014; Dodge & Simic, 2015).

WHAT HAVE YOU LEARNED?

Question 9.3

1. What visible changes take place in puberty?

For girls, the observable changes of puberty usually begin with nipple growth. Soon a few pubic hairs are visible, then peak growth spurt, widening of the hips, the first menstrual period (menarche), full pubic-hair pattern, and breast maturation. For boys, the usual sequence is growth of the testes, initial pubic-hair growth, growth of the penis, first ejaculation of seminal fluid, appearance of facial hair, peak growth spurt, deepening of the voice, and final pubic-hair growth.

Question 9.4

2. How do hormones affect the physical and psychological aspects of puberty?

In girls, estrogen triggers menarche and may contribute to depression. In boys, androgens produce sperm and trigger spermarche, and, in a small number of boys, may also contribute to the onset of schizophrenia. In both boys and girls, hormones awaken their interest in sex.

Question 9.5

3. Why might some high schools adopt later start times?

A phase delay in the sleep–wake cycles occurs in teens due to the hormones of the HPA axis during puberty. Thus, many teens are drowsy and have difficulty focusing in the morning. Adolescent learning is better in schools that start after 8 a.m.

Question 9.6

4. What is the connection between body fat and onset of puberty in girls and in boys?

Heavier girls reach menarche years earlier than malnourished girls do; most girls weigh at least 100 pounds before menarche. In boys, severe malnourishment always delays puberty, but body fat is not as influential.

Question 9.7

5. Why might early puberty be difficult for girls?

Early-maturing girls tend to have lower self-esteem, more depression, and poorer body image than do other girls. Because boys mature on average two years later than girls, they may tease an early-developing girl due to being unnerved by a sexual creature in their midst. Early-maturing girls also have more difficulties with self-image, tend to have older boyfriends, and are more susceptible to drug and alcohol abuse and domestic violence.

Question 9.8

6. What problems are common among early-maturing boys?

Early-maturing boys in the twenty-first century are more aggressive, more likely to break the law, and more likely to abuse drugs and alcohol.

Question 9.9

7. What are the sex differences in the growth spurt?

Girls experience their height growth spurt an average of two years before boys do. Girls’ height growth spurt usually precedes menarche, whereas boys’ height growth spurt usually follows spermarche.

Question 9.10

8. How do the skin and hair change during puberty?

The skin becomes oilier, sweatier, and more acne-prone. Hair becomes coarser and darker, and grows under the arms, on faces, and in the pubic area.

Question 9.11

9. What is the difference between primary and secondary sex characteristics?

Primary sex characteristics are directly involved in reproduction, whereas secondary sex characteristics signify that the body is capable of reproduction.

Question 9.12

10. What problems might occur if adolescents do not get enough iron or calcium?

Insufficient iron can cause anemia in adolescents, restricting muscle growth and strength. Insufficient calcium can lead to osteoporosis later in life.

Question 9.13

11. Why is body image often problematic in adolescence?

Few teenagers welcome every change puberty causes in their bodies. Instead, they tend to focus on and exaggerate imperfections. Few adolescents are happy with their bodies, partly because almost none look like the bodies portrayed in the media.

Question 9.14

12. What types of disordered eating are common in adolescence?

Overeating, eating erratically, or even ingesting drugs to lose weight is common among adolescents, especially girls. Boys may also overeat or eat erratically but are more likely to take steroids, creatine, etc. to increase their muscle mass.

Question 9.15

13. What are the differences among anorexia, bulimia, and binge eating disorder?

People suffering from anorexia nervosa refuse to eat normally because their body image is severely distorted; they may believe they are too fat when actually they are dangerously underweight. Those with bulimia consume thousands of calories but then vomit or use laxatives to control their weight, whereas those with binge eating disorder overeat without purging.