Chapter 14: Adolescence: Biosocial Development

sexual problems in adolescence

Before focusing on the hazards of adolescent sex, we should note that several "problems" are less troubling now than in earlier decades. Here are three specifics: 1. Teen births have decreased. In the United States, births to teenage mothers (aged 15 to 19) decreased 25 percent between 2007 and 2011 across race and ethnicity, with the biggest drop among Hispanic teens (J. Martin et al., 2010; Centers for Disease Control and Prevention, June 16, 2014). [The 2011 rate was the lowest in 40 years.] Similar declines are evident in other nations. The most dramatic results are from China, where the teen pregnancy rate was cut in half from 1960 to 2010 (reducing the 2015 projection of the world's population by about 1 billion). 2. The use of "protection" has risen. Contraception, particularly condom use among adolescent boys, has increased markedly in most nations since 1990 (Santelli & Melnikas, 2010). The U.S. Youth Risk Behavior Survey found that 63 percent of sexually active ninth-grade boys used a condom during their most recent intercourse (MMWR, June 10, 2016) (see Table 14.1). 3. The teen abortion rate is down. In general, the teen abortion rate in the United States has declined every year since abortion became legal. The rate today is about half that of 20 years earlier (Kost & Henshaw, 2013), even as the rate among older women has increased. **The reason is not only that intercourse is less frequent but also that contraception is more prevalent. These are positive trends, but many aspects of adolescent sexual activity remain problematic.

Diet Deficiencies

Deficiencies of iron, calcium, zinc, and other minerals are especially common during adolescence. -Because menstruation depletes iron, anemia is more common among adolescent girls than among any other age or sex group. -Boys everywhere may also be iron-deficient if they engage in physical labor or intensive sports: Muscles need iron for growth and strength. ^The cutoff for iron-deficiency anemia is higher for boys than for girls because boys require more iron to be healthy -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 that many contemporary teenagers will develop osteoporosis (fragile bones), a major cause of disability, injury, and death in late adulthood, especially for women. >Vitamin D deficient

Estrogens

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"

Too early, too late

For a society's health, early puberty is problematic: It increases the rate of emotional and behavioral problems. -For most adolescents, these links between puberty, stress, and hormones are irrelevant.

Sex too soon

However, compared to a century ago, adolescent sexual activity—especially if it results in birth—is more hazardous because four circumstances have changed: 1. Earlier puberty and weaker social taboos result in some very young teens having sex. Early sex correlates with depression, drug abuse, and lifelong problems (Kastbom et al., 2015). 2. If early sex leads to pregnancy and birth, most teenage girls have no partners to help. A century ago, teenage mothers were often married; now, in the United States, 86 percent are unwed (Shattuck & Kreider, 2013). 3. Raising a child has become more complex and expensive, and family helpers are scarce. The strategy that most teenage mothers used in former times—having their mother raise the child—is less readily available, as most young grandmothers are employed (Meyer, 2014). 4. Sexually transmitted infections are more common and more dangerous (Satterwhite et al., 2013).

primary sex characteristics

The parts of the body that are directly involved in reproduction, including the vagina, uterus, ovaries, testicles, and penis. -During puberty, every primary sex organ (the ovaries, the uterus, the penis, and the testes) increases dramatically in size and matures in function. Reproduction becomes possible.

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. - 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. Growth is not always symmetrical: One foot, one breast, or even one ear may grow later than the other

Puberty

The time between the first onrush of hormones and full adult physical development. Puberty usually lasts three to five years. Many more years are required to achieve psychosocial maturity. -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. -The process normally starts sometime between ages 8 and 14. Most biological growth and maturation ends about four years after the first signs appear, although some individuals (especially boys) add height, weight, and muscle until age 20 or so.

adrenal glands

Two glands, located above the kidneys, that respond to the pituitary, producing hormones.

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. -typical at 13

Body fat and chemicals

-Another influence on the onset of puberty is body fat, which itself is partly genetic and partly cultural. ^Heavy girls (over 100 pounds) reach menarche years earlier than thinner ones do, especially if girls are underweight because of malnutrition. ex./ Malnutrition explains why youths reach puberty later in some parts of Africa, while their genetic relatives in North America mature much earlier. ^ For example, girls in northern Ghana reach menarche more than a year later (almost age 14) than African American girls in the United States (just past 12). Ghanaian girls in rural areas—where malnutrition is more common—are behind those in urban areas

Boys

-Early maturation is more harmful than helpful for females no matter when they were born, but cohort matters for males. -Early-maturing boys who were born around 1930 often became leaders in high school and earned more money as adults -In the twenty-first century, early-maturing boys are more aggressive, law-breaking, and alcohol-abusing than the average boy -A boy with rapidly increasing testosterone, whose body looks more like a man than a child, whose brain is more affected by emotions than logic, and who seeks approval from peers more than adults, is likely to trouble parents, peers, schools, and the police. -Early puberty is particularly stressful if it happens suddenly: The boys most likely to become depressed are those for whom puberty was both early and quick -In adolescence, depression is often masked as anger. That fuming, flailing 12-year-old may be more sad than mad. -Late puberty may also be difficult, especially for boys. ^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. >If a 14-year-old boy still looks childish, he may react in ways (clowning, fighting, isolating) that are not healthy for him.

Girls

-Early-maturing girls tend to have lower self-esteem, more depression, and poorer body image than do other girls -Some early-maturing girls have older boyfriends, who are attracted to their womanly shape and girlish innocence. ^Having an older boyfriend bestows status among young adolescents, but it also increases the rate of drug and alcohol use - Early-maturing girls enter abusive relationships more often than other girls do.

Brain maturation

-However, the usual sequence of brain maturation, propelled by hormones that activate the limbic system at puberty, can lead to danger. -The prefrontal cortex matures steadily, advancing gradually year by year. The limbic system, however, is affected more by hormones (the HPG axis) and thus grows dramatically in early adolescence. Consequently, for contemporary teenagers, emotions may overwhelm rational thought for a decade. - The limbic system makes powerful sensations—loud music, speeding cars, strong drugs—compelling. -Pubertal hormones target the amygdala directly (Romeo, 2013). The instinctual and emotional areas of the adolescent brain develop ahead of the reflective, analytic areas. ^Puberty means emotional rushes, unchecked by caution. >Immediate impulses thwart long-term planning and reflection. -It is not that the prefrontal cortex shuts down. Actually, it continues to develop throughout adolescence and beyond. ^ Maturation doesn't stop, but the balance and coordination between the various parts of the brain are off-kilter -When stress, arousal, passion, sensory bombardment, drug intoxication, or deprivation is extreme, the adolescent brain is flooded with impulses that overwhelm the cortex and might shame an adult.

sexual activity

-Masturbation is common in both sexes, for instance. One cross-sectional study of 14- to 17-year-olds in the United States reported that 74 percent of the boys and 48 percent of the girls said they masturbated -Emotions regarding sexual experience, like the rest of puberty, are strongly influenced by social norms. -Then, girls were supposed to slow down the boys' advances. This was called the double standard, in that behaviors of boys and girls were held to different standards. ^Many adolescents still expect boys and girls to approach heterosexual interactions differently, with boys more insistent and girls more hesitant. ex./For example, among high school seniors, 57 percent of the girls and 59 percent of the boys have had sexual intercourse, with most of them sexually active in the past three months. -In the United States, every gender, ethnic, and age group is less sexually active than the previous cohort. ^Many reasons for the trends have been suggested: better sex education, fear of HIV/AIDS, new realization of the problems of pregnancy, better understanding of abortion, less male-female intimacy . . . more research is needed.

Life span perspectives of eating disorders

-The origins begin much earlier, in family eating patterns if parents do not help their children eat sensibly—when they are hungry, without food being a punishment or a reward. -During the teen years, many parents do not recognize serious eating disorders, and thus they delay getting the help that their children need -Perhaps 5 percent die of anorexia—death usually coming 10 years or more after initial symptoms. ^Most survive but experience depression and anxiety or health complications such as heart disease, infertility, or osteoporosis.

Ethnic Differences

-Well-nourished Africans tend to experience puberty a few months earlier and Asians a few months later than Europeans, but they all function well if their peers are on the same schedule -European research finds that early-maturing Swedish girls were likely to encounter problems with boys and early drug abuse, but similar Slovak girls were not, presumably because parents and social norms kept Slovak girls under tight control (Skoog & Stattin, 2014). ^Finally, early-maturing Mexican American boys were likely to experience trouble (with police and with peers) if they lived in neighborhoods with few Mexican Americans, but not if they lived in ethnic enclaves

Sleep studies

1. Some municipalities also fight adolescent biology. In 2014, Baltimore implemented a law that requires everyone under age 14 to be home by 9 P.M., and 14- to 16-year-olds to be off the streets by 10 P.M. on school nights and 11 P.M. on weekends. -This assumes that home is a happy, safe place where teenagers will go to sleep early, and it restricts the teen's ability to socialize or study with friends. 2. Several enlightened school districts have revised their schedules. Minneapolis high schools changed their start time from 7:15 A.M. to 8:40 A.M.; 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 A.M. to an average of 8:30 A.M. -Unexpected advantages appeared: more efficient energy use, less adolescent depression, fewer visits to the school nurse, and in Tulsa, unprecedented athletic championships. 3.They have new motivation. In August 2014, the American Academy of Pediatrics concluded that high schools should not begin until 8:30 or 9 A.M., because adolescent sleep deprivation causes a cascade of intellectual, behavioral, and health problems. -The doctors noted that 43 percent of high schools in the United States start before 8 A.M. -Most developmentalists, pediatricians, and education researchers wonder why adult traditions are preserved while adolescent learning is ignored.

sequence of growth

1. weight growth: Exactly when, where, and how much weight they gain depends on heredity, hormones, diet, exercise, and sex. -By age 17, the average girl has twice the percentage of body fat as her male classmate, whose increased weight is mostly muscle. 2. height: A height spurt follows the weight spurt; a year or two later a muscle spurt occurs. -Thus, the pudginess and clumsiness of early puberty are usually gone by late adolescence. 3. muscle: At puberty, all of the muscles grow. -Arm muscles develop particularly in boys, doubling in strength from age 8 to 18. -Other muscles are gender-neutral. ex./ For instance, both sexes run faster with each year of adolescence, with boys not much faster than girls

circadian rhythm

A day-night cycle of biological activity that occurs approximately every 24 hours. -For most people, daylight awakens the brain. That's why people experiencing jet lag are urged to take an early-morning walk. ^But at puberty, night may be more energizing, making some teens wide awake and hungry at midnight but half asleep, with no appetite or energy, all morning. -In addition to circadian changes at puberty, some individuals (especially males) are naturally more alert in the evening than in the morning, a genetic trait called eveningness. ^Puberty plus eveningness increases risk (drugs, sex, delinquency), in part because teenagers are awake when adults are asleep. -Added to the circadian sleep debt, "the blue spectrum light from TV, computer, and personal-device screens may have particularly strong effects on the human circadian system" -Sleep deprivation and irregular sleep schedules increase several proven dangers, including insomnia, nightmares, mood disorders (depression, conduct disorder, anxiety), and falling asleep while driving.

sexually transmitted infection (STI)

A disease spread by sexual contact, including syphilis, gonorrhea, genital herpes, chlamydia, and HIV. -In the United States, half of all new STIs occur in people ages 15 to 25, even though this age group has less than one-fourth of the sexually active people -Chlamydia is the most frequently reported one; it often begins without symptoms, yet it can cause permanent infertility. -Worse is human papillomavirus (HPV), which has no immediate consequences but increases the risk of "serious, life-threatening cancer" in both sexes ^ Immunization before the first intercourse has reduced the rate of HPV, but in 2013 among 13- to 17-year-olds, only 38 percent of the girls and 14 percent of the boys had all three recommended doses -

menarche

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

Pituitary

A gland in the brain that responds to a signal from the hypothalamus by producing many hormones, including those that regulate growth and sexual maturation.

Leptin

A hormone that affects appetite and is believed to affect the onset of puberty. Leptin levels increase during childhood and peak at around age 12. -Leptin is essential for appetite, energy, and puberty. However, too much leptin correlates with obesity, early puberty, and then early termination of growth. ^Thus, the heaviest third-grade girl may become the tallest fifth-grader and then the shortest high school graduate.

Body image

A person's idea of how his or her body looks. -Two-thirds of U.S. high school girls are trying to lose weight, one-third think they are overweight, and only one-sixth are actually overweight or obese -Few adolescents are happy with their bodies, partly because very few look like the bodies portrayed online and in magazines, movies, and television programs that are marketed to teenagers -Dissatisfaction with body image is not only depressing but also can be dangerous. Many teenagers eat erratically and take drugs to change their bodies.

HPA (hypothalamus-pituitary-adrenal) axis

A sequence of hormone production originating in the hypothalamus and moving to the pituitary and then to the adrenal glands.

HPG (hypothalamus-pituitary-gonad) axis

A sequence of hormone production originating in the hypothalamus and moving to the pituitary and then to the gonads.

estradiol

A sex hormone, considered the chief estrogen. Females produce much more estradiol than males do.

bulimia nervosa

An eating disorder characterized by binge eating and subsequent purging, usually by induced vomiting and/or use of laxatives. -This disorder is clinically present in 1 to 3 percent of female teenagers and young adults in the United States. They overeat compulsively, consuming thousands of calories within an hour or two, and then purge through vomiting or laxatives. -A disorder that is newly recognized in DSM-5 is binge eating disorder. ^Some adolescents periodically and compulsively overeat, quickly consuming large amounts of ice cream, cake, or any snack food until their stomachs hurt. ^When bingeing becomes a disorder, overeating is typically done in private, at least weekly for several months. > The sufferer does not purge (hence this is not bulimia) but feels out of control, distressed, and depressed.

anorexia nervosa

An eating disorder characterized by self-starvation. Affected individuals voluntarily undereat and often overexercise, depriving their vital organs of nutrition. Anorexia can be fatal. - Certain alleles increase the risk of developing anorexia (Young, 2010), with higher risk among girls with close relatives who suffer from eating disorders or severe depression.

child sexual abuse

Any erotic activity that arouses an adult and excites, shames, or confuses a child, whether or not the victim protests and whether or not genital contact is involved. -defined as any sexual activity (including fondling and photographing) between a juvenile and an adult, with age 18 the usual demarcation (although legal age varies by state). ^Girls are particularly vulnerable, although boys are also at risk. -The rate of sexual abuse increases at puberty, a particularly sensitive time because many young adolescents are confused about their own sexual urges and identity. ^Virtually every adolescent problem, including pregnancy, drug abuse, eating disorders, and suicide, is more frequent in adolescents who are sexually abused. -Adolescent girls are common victims of sex trafficking, not only because their youth makes them more alluring but also because their immaturity makes them more vulnerable

Organ Growth

In both sexes, lungs triple in weight; consequently, adolescents breathe more deeply and slowly. -The heart (another muscle) doubles in size as the heartbeat slows, decreasing the pulse rate while increasing blood pressure -Red blood cells increase in both sexes, but dramatically more so in boys, which aids oxygen transport during intense exercise. -height spurt precedes increases in bone mass, making young adolescents particularly vulnerable to fractures -One organ system, the lymphoid system (which includes the tonsils and adenoids), decreases in size, so teenagers are less susceptible to respiratory ailments. ^Mild asthma, for example, often switches off at puberty—half as many teenagers as children are asthmatic -This reduction in susceptibility is aided by growth of the larynx, which also deepens the voice, dramatically noticeable in boys. -Another organ system, the skin, becomes oilier, sweatier, and more prone to acne. Hair also changes, becoming coarser and darker. -New hair grows under arms, on faces, and over sex organs (pubic hair, from the same Latin root as puberty).

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. -Those female curves are often considered signs of womanhood, but neither breasts nor wide hips are required for conception; thus, they are secondary, not primary, sex characteristics. -The pattern of hair growth at the scalp line (widow's peak), the prominence of the larynx (Adam's apple), and several other anatomical features differ for men and women; all are secondary sex characteristics that few people notice.

genes and gender

Sex affects sequence as well. -The female height spurt occurs before menarche; the male increase in height occurs after spermarche. ^Therefore, unlike height, for hormonal and sexual changes, girls are less than a year ahead of boys. ^This means that 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. -Overall, about two-thirds of the variation in age of puberty is genetic—not only the genes associated with the XX or XY chromosomes but also in the genes common in families and ethnic groups. ^ If both of a child's parents were early or late to reach puberty, the child will likely be early or late as well. -On average, African Americans reach puberty about seven months before European or Hispanic Americans; Chinese Americans average several months later. ^The significance of all these changes is more gender than sex, more cultural than genetic.

Stress

Stress hastens puberty, especially if a child's parents are sick, drug-addicted, or divorced, or if the neighborhood is violent and impoverished. ex./One study of sexually abused girls found that they began puberty seven months earlier, on average, than did a matched comparison group

secular trend

The long-term upward or downward direction of a certain set of statistical measurements, as opposed to a smaller, shorter cyclical variation. ex./As an example, over the last two centuries, because of improved nutrition and medical care, children have tended to reach their adult height earlier and their adult height has increased.

gonads

The paired sex glands (ovaries in females, testicles in males). The gonads produce hormones and mature gametes. -The activated gonads soon produce mature ova or sperm, released in menarche or spermarche. Conception is possible, although peak fertility occurs four to six years later.

Hormones

body chemicals that regulate hunger, sleep, moods, stress, sexual desire, immunity, reproduction, and many other bodily functions and processes, including puberty. -Throughout adolescence, hormone levels correlate with physiological changes and self-reported developments -Hormonal increases may also that precipitate psychopathology. In both genders, adolescence is the peak time for the emergence of many disorders. ^The rush of hormones at puberty puts some vulnerable children over the edge, although hormones are never the sole cause >Probably because of sex differences in hormones, adolescent males are almost twice as likely as females to develop schizophrenia, and females are more than twice as likely to become severely depressed -Hormones also direct adolescents toward typical sexual roles and interactions, perhaps a product of selective fitness for the human species. ^ Of course, sexual identity and gender roles are increasingly complex, because of the combination of puberty, norms, and variations—a topic -Although emotional surges, nurturant impulses, and lustful urges arise with hormones, remember that body, brain, and behavior always interact. ^Sexual thoughts themselves can cause physiological and neurological processes, not just result from them. >Cortisol levels rise at puberty, and that makes adolescents quicker to become angry or upset ex./ For example, when people react to emerging breasts or beards, those reactions evoke adolescent thoughts and frustrations, which then raise hormone levels, propel physiological development, and trigger more emotions.