Chapter 17– Emerging
Adulthood:
Biosocial Development
The period between the ages of 18 and 25, which is now
widely thought of as a separate developmental stage.
Growth and Strength
Strong and Active Bodies
• Emerging adults are usually in good health.
• Traditionally, ages 18 and 25 were a time for
hard physical work and childbearing.
• Physical work and parenthood are no longer
expected of every young adult in the 21st
century.
Growth and Strength
• Because of food availability, most emerging
adults have reached full height (girls usually by
age 16, boys by age 18).
• Muscle growth and fat accumulation continue into
the early 20s, when women attain adult breast
and hip size and men reach full shoulder width
and upper-arm strength.
• Death from disease almost never occurs during
emerging adulthood.
Bodies Designed for Health
• By age 20, the immune system is well-developed
• Usually, blood pressure is normal, teeth develop
no new cavities, heart rate is steady, the brain is
fully grown, and lung capacity is as large as it will
ever be.
• Senescence
– The process of aging, whereby the body becomes
less strong and efficient.
– Begins in late adolescence
Growth and Strength
Bodies in Balance
Homeostasis
• The adjustment of all the body’s systems to
keep physiological functions in a state of
equilibrium.
• As the body ages, it takes longer for these
adjustments to occur, so it becomes harder
for older bodies to adapt to stress.
• Nutrition and exercise underlie health at every
age.
Unused Potential
• Organ reserve
– The capacity of organs to allow the body to
cope with stress, via extra, unused functioning
ability.
• Maximum strength potential
– Begins to decline by age 25
– Fifty-year-olds retain 90% of muscle reserve
they had at age 20
Sexual Activity
• The sexual-reproductive system is especially
vigorous during emerging adulthood.
• The sex drive is powerful, infertility is rare,
orgasm is frequent, and birth is easy, with
fewer complications in the early 20s than at
any other time.
• Sexual-reproductive characteristics are
produced by sex hormones, which peak in
both sexes at about age 20.
Growth and Strength
• With frequent intercourse and without
contraception, the average woman in her early
20s becomes pregnant within three months.
• Globalization, advanced technology, and modern
medicine have combined to produce effective
contraception, available in almost every nation.
• As fewer infants die, people no longer need to
begin childbearing before age 20 or have four or
more children simply to ensure that some children
will survive.
Growth and Strength
• Advances in contraception have reduced the
birth rate and have also increased the rate of
sexual activity, especially among unmarried
adults.
• Globally, emerging adults have fewer babies
but engage in more sexual activity than older
adults (married or not) or than people their
own age once did.
• Half of all emerging adults in the United
States have had at least one sexually
transmitted infection (STI).
Emotional Stress
• One consequence of current sexual patterns may be
emotional stress as relationships begin and end.
• Attitudes about the purpose of sex (Laumann &
Michael):
– Reproduction
– Relationship
– Recreation
• If partners have differing ideas about the purpose of
sex or the nature of gender, emotional pain and
frustration can occur.
Sexually Transmitted Infections
(STIs)
• STIs have always been present but the rate has
reached epidemic proportions due to sexual
patterns.
• Best way to prevent STIs is lifelong monogamy.
• Worldwide, globalization fuels every contagious
disease.
Psychopathology
• Incidence of psychopathology increases in
emerging adulthood.
• Rate of serious mental illness is almost double
that for adults over age 25.
• Diathesis-stress model
– View that mental disorders are produced by the
interaction of genetics (diathesis) and a stressful
environment and life events.
Mood Disorders
Bipolar Disorder
• May begin in childhood but becomes more
severe in adulthood.
Depression
• Most common mood disorder
• A loss of interest or pleasure for 2 weeks or
more.
• May be rooted in imbalances in neurotransmitters
and hormones
Anxiety Disorders
•
•
•
•
Evident in ¼ of all U.S. residents below 25
Panic attacks, PTSD, and OCD
More common, worldwide than depression
Age and genetics shape the symptoms
• Hikikomori
– Common among young adults in Japan
– Victims isolate themselves for months or years
Schizophrenia
• About 1% of adults have schizophrenia
• Disorganized and bizarre thoughts,
delusions, hallucinations, and emotions
• Risk factors: genetic, malnutrition when
brain is developing, social pressure.
• Symptoms usually begin in adolescence
Exercise
• Reduces blood pressure, strengthens the heart
& lungs.
• Makes depression, osteoporosis, heart disease,
arthritis and some cancers less likely.
• Those who are not fit during emerging adulthood
are 4 times more likely to have diabetes and
high blood pressure 15 years later.
Eating Well
• At every stage of life, diet affects future
development
• Set point
– A certain body weight that a person’s homeostatic
processes strive to maintain.
• Body mass index (BMI)
– The ratio of a person’s weight in kilograms divided by
their height in meters squared.
Eating Well
Taking Risks
• Emerging adulthood is marked by a greater
willingness to take risks of all sorts, not just
sexual ones.
• Young adults enjoy
danger, drive without
seat belts, carry guns,
try addictive drugs.
Taking Risks
• Edgework
–Occupations, recreational activities, or
other ventures that involve a degree of risk
or danger.
–The prospect of “living on the edge” makes
edgework compelling to some individuals.
• Extreme sports
–Forms of recreation that include apparent
risk of injury or death and that are attractive
and thrilling as a result.
Drug Abuse
• Drug abuse
– The ingestion of a drug to the extent that it
impairs the user’s biological or psychological
well-being.
• Drug addiction
– A condition of drug dependence in which the
absence of the given drug from the
individual’s system produces a drive—
physiological, biological, or both—to ingest
more of the drug.
Drug Abuse
Drug Abuse
• Drug abuse is particularly common among
those who die violently.
• In the U.S., between the ages of 15 and 25,
almost 1 male in every 100 dies violently,
through suicide, homicide, or a motor-vehicle
accident.
• About 4 times as many young men as young
women commit suicide or die in motor-vehicle
accidents, and 6 times as many are
murdered.
A Way to Curb Alcohol Abuse in
College
Social norms approach
• A method of reducing risky behavior among
emerging adults that is based on their desire
to follow social norms.
• This approach publicizes survey results to
make emerging adults aware of the actual
prevalence of various behaviors within their
peer group.