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Adolescence: Biosocial Development

The Developing Person Through Childhood and Adolescence

Kathleen Stassen Berger | Eleventh Edition

Chapter 14

WHAT WILL YOU KNOW?

How can you predict when puberty will begin for a particular child?

Why do some teenagers avoid eating for days, even months?

What makes teenage sex a problem instead of a joy?

Puberty Begins

Puberty in the United States

Time between the first onrush of hormones and full adult physical development

Usually starts between 8 and 14 years; marked variation

Maturation delays start; stress advances it

Puberty

Menarche

Girl’s first menstrual period, signaling that she has begun ovulation

Pregnancy is biologically possible, but ovulation and menstruation often irregular for years after menarche.

Spermarche

Boy’s first ejaculation of sperm

Erections can occur as early as infancy, but ejaculation signals sperm production.

Puberty: Unseen Beginnings (part 1)

The entire process of puberty begins with an invisible event—a marked increase in hormones.

Hormone

Organic chemical substance that is produced by one body tissue and conveyed via the bloodstream to another to affect some physiological function

HPA (hypothalamus–pituitary–adrenal) axis

Sequence of a chain reaction of hormone production, originating in the hypothalamus and moving to the pituitary and then to the adrenal glands

Puberty: Unseen Beginnings (part 2)

The pituitary produces hormones that stimulate the adrenal glands.

Pituitary

Gland in the brain that responds to a signal from the hypothalamus by producing many hormones, including those that regulate growth and control other glands, among them the adrenal and sex glands

Adrenal glands

Two glands, located above the kidneys, that produce hormones including the “stress hormones” epinephrine (adrenaline) and norepinephrine

Biological Sequence of Puberty

Puberty begins with a hormonal signal from the hypothalamus to the pituitary gland, both deep within the brain. The pituitary, in turn, sends a hormonal message through the bloodstream to the adrenal glands and the gonads to produce more hormones.

Sex Hormones (part 1)

Gonads

Paired sex glands (ovaries in females, testicles in males)

Gonads produce hormones and gametes.

HPG (hypothalamus–pituitary–gonad) axis

Sequence of hormone production that originates in the hypothalamus, moves to the pituitary, and then to the gonads

Sex Hormones (part 2)

GnRH (gonadotropin-releasing hormone)

Hormones that causes gonads to enlarge and increase production (estradiol in girls; testosterone in boys)

Estradiol

Sex hormone, considered the chief estrogen

Females produce more estradiol than males do.

Testosterone

Sex hormone, the best known of the androgens (male hormones).

Males secrete far greater amounts of testosterone than females do.

Sex Hormones (part 3)

Hormonal increase may precipitate psychopathology

Peak time in both genders for disorder emergence.

Males: Schizophrenia twice more likely in males

Females: Severe depression twice more likely in females

Psychotherapy during adolescence is often successful.

Bodies, brains, and behavior all affect one another.

Body Rhythms

Hypothalamus and the pituitary regulate the hormones that affect the biorhythms of stress, appetite, sleep.

In puberty, a phase delay in circadian sleep-wake cycles (circadian rhythm) may occur,

Eveningness puts adolescents at risk for antisocial activities and sleep deprivation,

Blue spectrum lights from electronic devices may have strong effects on human circadian system by interfering with nighttime sleepiness.

The phase delay at puberty makes many teens wide awake and hungry at midnight but half asleep, with no appetite or energy, all morning.

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

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, as almost all do. Then all day they are tired

Sleep deprivation and irregular sleep schedules increase several proven dangers, including insomnia, nightmares, mood disorders (depression, conduct disorder, anxiety), and falling asleep while driving. Adolescents are particularly vulnerable to all of these, and sleepiness makes it worse (see Figure 14. 2 ). In addition, sleepy students do not learn as well as well-rested ones.

Getting to School on Time!

Sleep-deprived teenagers nod off in class and sometimes use drugs to stay awake or go to sleep.

In August 2014, the American Academy of Pediatrics concluded that high school should not begin until 8:30 a.m. or 9 a.m. because adolescent sleep deprivation causes a cascade of intellectual and behavioral problems

Do you agree? Disagree? Why?

For many adolescents, early sleep and early rising are almost impossible.

Brain Growth

Different parts of the brain grow at

different rates.

The limbic system (fear, emotional impulses) matures before the prefrontal cortex (planning ahead, emotional regulation).

Instinctual and emotional areas develop before the reflective ones do.

Brain scans confirm that emotional control, revealed by fMRI studies, is not fully developed until adulthood, because the prefrontal cortex is limited in connections and engagement.

Same People, But Not the Same Brain

These brain scans are part of a longitudinal study that repeatedly compares the proportion of gray matter from childhood through adolescence. Gray matter is reduced as white matter increases, in part because pruning during the teen years (the last two pairs of images here) allows intellectual connections to build. As the authors of one study that included this chart explain, teenagers may “look like an adult, but cognitively they are not there yet” (K. Powell, 2006, p. 865).

Benefits of Adolescent Brain Development

There are benefits as well as hazards in the adolescent brain.

Increased myelination and slower inhibition make reactions lightning fast.

The brain’s reward areas activate positive neurotransmitters, and teenagers become happier.

Questioning assumptions can raise important issues.

Risk taking often facilitates learning.

Synaptic growth enhances moral development.

Genes and Gender (part 1)

About two-thirds of the variation in age of puberty is genetic.

Genes on the sex chromosomes have a marked effect on age of puberty.

Girls generally develop ahead of boys.

The female height spurt occurs before menarche, whereas for boys the increase in height is relatively late, after spermarche.

On average, African Americans reach puberty about seven months before European or Hispanic Americans; Chinese Americans average several months later.

The female height spurt occurs before menarche, whereas for boys the increase in height is relatively late, after spermarche.

Genes and Gender (part 2)

One of the best qualities of adolescents is that they identify more with their generation than their ethnic group.

Children who have a relatively large proportion of body fat experience puberty sooner than do their thin contemporaries. Globally urban children are more often overfed and underexercised than rural children

Do the expressions of these 13-year-olds convey respect or hostility? Impossible to be sure, but given that they are both about mid-puberty (face shape, height, shoulder size), and both in the same school, they may become friends.

If a child’s genes, gender, body fat, and stress level are known, some prediction is possible.

Most girls must weigh at least 100 pounds before experiencing first period

Body Fat and Chemicals (part 1)

Secular trend

Data on puberty over the centuries that reveals a dramatic example of a long-term statistical increase or decrease.

Each generation has experienced puberty a few weeks earlier and has grown a centimeter or so taller, than did the preceding one.

Secular trend has stopped in developed nations.

Do you know why?

Some research finds, however, that puberty is delayed, not accelerated, in boys who were exposed to phthalates and bisphenol A when they were in the womb (Ferguson et al., 2014) or who experience heavy doses of pesticides in boyhood.

Body Fat and Chemicals (part 2)

Chemicals

Research on the effects on humans of hormones and other chemicals, whether natural or artificial, is complex.

Female system is especially sensitive to leptin and other factors in the environment.

Leptin

Affects appetite and is believed to be involved in the onset of puberty

Increases during childhood and peaks at around age 12

Evokes uncertainty about its effects

In both sexes, chronic malnutrition delays puberty.

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.

Stress and Puberty

Several longitudinal studies show a direct link between stress and puberty.

Harsh parenting increases cortisol levels, which affects puberty thus increasing sexual risk, but not other risks (Belsky and colleagues).

Evolutionary theorists suggest there was a shaping of the genome over millennia.

Affects children who are genetically sensitive to context

Makes reproduction more difficult in adulthood and hastens hormonal onset of puberty

Too Early, Too Late

Girls

Early-maturing girls tend to have lower self-esteem, more depression, and poorer body image than later-maturing girls.

Early-maturing girls may be attracted to older boyfriends and enter into abusive relationships more often than other girls.

Boys

Early-maturing boys are more aggressive, law-breaking, and alcohol-abusing than later-maturing boys.

Slow developing boys tend to be more anxious, depressed, and afraid of sex.

Size and maturation are important for many adolescents in every nation.

Ethnic Differences

The effects of early puberty vary not only by sex, but also by ethnicity and culture.

In contrast to European Americans, early-maturing African American girls were not depressed, but early-maturing African American boys were.

European research finds that Swedish early-maturing girls were likely to encounter problems with boys and early drug abuse, but similar Slovak girls were not.

Early maturing Mexican American boys were likely to experience trouble with the police and with other boys if they lived in neighborhoods with relatively few Mexican-Americans, but not if they lived in ethnic enclaves.

None of these trends is true for all children, of course, as ethnicity is only one influence on development. However, all three studies confirm that contextual factors interact with biological ones, and both have significant implications for individuals. Relationships with peers and parents make off-time puberty better or worse.

Growing Bigger and Stronger (part 1)

Growth spurt

“Spurt” is a relatively sudden and rapid physical growth that occurs during puberty.

Each body part increases in size on a schedule; growth is not always symmetrical.

Weight usually precedes height, and growth of the limbs precedes growth of the torso.

Growing Bigger and Stronger (part 2)

Sequence: Weight, height, muscles

Height spurt follows weight spurt, then a year or two later a muscle spurt occurs.

Arm muscles develop more in boys; other muscles are gender-neutral.

Growing Bigger and Stronger (part 3)

Little difference

Both sexes develop longer and stronger legs during puberty.

Growing Bigger and Stronger (part 4)

Organ growth

Lungs triple in weight; consequently, adolescents breathe more deeply and slowly.

Heart doubles in size and the heartbeat slows, decreasing the pulse rate while increasing blood pressure.

Only lymphoid system decreases in size.

Only lymphoid system (which includes the tonsils and adenoids), decreases in size. Teenagers are less susceptible to respiratory ailments.

Growing Bigger and Stronger (part 5)

Skin and hair

Skin becomes oilier, sweatier, and more prone to acne.

Hair on the head and limbs becomes coarser and darker.

New hair grows under arms, on the face, and over sex organs.

In many ways, hair is more than a growth characteristic; it becomes a display of sexuality.

Growth and Nutrition

Diet deficiencies

In 2015, only 16 percent of U.S. high school seniors ate recommended three or more daily vegetable servings.

Deficiencies of iron, calcium, zinc, and other minerals are cause for concern, since these are needed for bone and muscle growth.

Nutritional deficiencies result from the food choices that young adolescents are allowed, even enticed, to make.

Deficiencies of iron, calcium, zinc, and other minerals may be even more problematic during adolescence than vitamin deficiencies, since minerals are needed for bone and muscle growth.

Choices Made

Nutritional deficiencies result from the food choices that young adolescents are enticed to make.

These choices are influenced by:

Fast-food establishments

Price of healthy versus unhealthy choices

School-based vending machines

Diet Worldwide: adolescent obesity is increasing. Parental responses differ, from indifference to major focus. 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).

Body Image

Anxiety about body image contributes to poor nutrition among teenagers.

Focus on and exaggeration of imperfections

Few adolescents are happy with their bodies.

Discrepancy between teen body and bodies portrayed online and in teen-marketed media

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.

Dissatisfaction with body image is not only depressing but also can be dangerous. Many teenagers eat erratically and take drugs to change their bodies. 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).

Eating Disorders

Anorexia nervosa

Eating disorder characterized by self-starvation

Affected individuals voluntarily undereat and often over exercise, depriving their vital organs of nutrition; anorexia can be fatal.

Bulimia nervosa

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

Binge-eating disorder

The DSM-5 introduced binge-eating disorder as a diagnostic category, in part to recognize that bingeing is sometimes associated with anorexia.

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.

According to the DSM-5, anorexia is officially diagnosed when three symptoms are evident:

significantly low body weight for developmental stage (BMI of 17 or lower)

intense fear of weight gain

disturbed body perception and denial of the problem

According to the DSM-5, bulimia is officially diagnosed when three symptoms are evident:

bingeing and purging at least once a week for three months

uncontrollable urges to overeat

sense of self inordinately tied to body shape and weight

Life-Span Causes and Consequences

Origins of disordered eating

Cultural image

Stress

Puberty

Hormones

Childhood patterns

Family patterns and eating disorder reduction

Healthy eating in childhood

Eating together during childhood

An eating disorder is characterized by severe calorie restriction and the fear of being fat. Affected individuals undereat, or overeat and the purge, depriving their vital organs of nutrition. Anorexia can be fatal

Sexual Maturation

Primary sex characteristics

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

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.

Sexual Activity (part 1)

Boys tend to be somewhat more sexually experienced than girls during the high school years.

Since the Youth Risk Behavior Survey began in 1991, the overall trend has been toward equality in rates of sexual activity.

Boys are more influenced by hormones and girls by culture.

Both are influenced by hormones, society, biology, and culture.

Universal experience (rising hormones) that produces another universal experience (growth of primary and secondary sex characteristics) is influenced by cohort, gender, and culture.

Among young European Americans, those girls with lower self-esteem were more likely to engage in sexual intimacy.

Gender gap between rates of sexual activity is narrowing within the United States and among other nations.

Sexual Activity (part 2)

Universal experience that produces another universal experience is influenced by cohort, gender, and culture.

Masturbation is common in both sexes.

Social gender norms are powerful; double standard is less powerful.

Almost equal levels of sexual activity, but boys report higher partner number.

Research finds that the most powerful influence on adolescents’ sexual activity is their close friends, not national or local norms for their gender or their ethnic group.

Sexual Problems in Adolescence

Problems less than in earlier decades

Positive trends

Decreased teen births in every nation

Rise in use of protection

Decrease in teen abortion rate

Sex Too Soon

Hazards related to adolescent sexual activity

Correlation of early sex with depression, drug abuse, and lifelong problems

Absence of partner

Increased complexity and expense related to parenting; fewer family helpers

More common and dangerous STIs

Sexual Abuse

Child sexual abuse

Definition

Most common time

International and national rates

Characteristics

Family members are most likely to abuse.

Victims are often isolated and uninformed.

Almost all adolescent problems, more frequent in abused

Impact of abuse often continues into adulthood

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 made.

Sex Trafficking

Adolescent girls are the most common victims.

United States estimates range from 1,000–336,000 victims.

Could this happen to someone in your community?

Sexually Transmitted Infections

Worldwide, sexually active teenagers have higher rates of most common STIs: gonorrhea, genital herpes, and chlamydia.

Human papillomavirus (HPV) has no immediate consequences but increases the risk of serious, life-threatening cancer in both sexes; the rate is reduced by immunization.

Early age of first intercourse, failure to use condoms, hesitancy to report infection all contribute to high U.S. infection rate.

Sexually transmitted infection (STI): a disease spread by sexual contact, including syphilis, gonorrhea, genital herpes, chlamydia, and HIV.

HPV infection can have negative consequences after adolescent years.