Early Adulthood: Body, Mind, and Path

This is Unit Eleven, part one, on emerging adulthood, the body at its peak, health and risk, and sexuality. Unit Ten closed on teen employment. Unit Eleven opens early adulthood, starting with a decade some researchers call a new stage of life. Carry one question through this part: is emerging adulthood a universal stage, or a circumstance of some lives? At the entry that weighs the question directly, the part's answer is a period many young people in affluent societies pass through, shaped by education, economics and culture. By the end you will be able to name Arnett's five features. To state the criticisms of emerging adulthood as a stage. To match adrenaline and cortisol to their effects. To assign a drug to its class. And to state when most mental disorders begin.

Eight entries on emerging adulthood: its features, how class and culture change it, and whether it is a stage at all. The opening question is answered here.

Arnett's new period.

HGD 1501 Emerging Adulthood

Emerging adulthood, Jeffrey Arnett's term, is the first phase of early adulthood, roughly eighteen to twenty-five, a period of intense exploration of work, beliefs and relationships, like a twenty-two-year-old changing jobs, cities and partners. In many countries it acts as a buffer before full adult roles; some researchers extend it to twenty-nine.

Arnett's five features.

HGD 1502 Arnett's Five Features

Arnett described five features. Identity exploration: trying out possibilities in love and work. Instability: frequent changes of residence, job and relationships. Self-focus: fewer obligations to others. Feeling in-between: neither adolescent nor fully adult. The age of possibilities: optimism about the future, even amid difficulty. A twenty-four-year-old who says she is sort of an adult, has moved three times in two years, and is sure life will turn out well shows three of them. Emerging adulthood is found mainly in industrialized countries, where most young people attend tertiary education and marry and have children around thirty.

Marcia's statuses, in adulthood.

HGD 1503 Marcia's Statuses in Adulthood

Marcia's statuses continue in adulthood, can come in any order, and differ by domain: a student may be in moratorium on her major while having achieved her faith. Achievement goes with self-esteem, conscientiousness and problem-focused coping, though diffusion may be a natural starting point, and achievement is not feasible or ideal in every setting.

Class, and emerging adulthood.

HGD 1504 Class and Emerging Adulthood

Emerging adulthood occurs across social classes but differently: lower income brings short-term work, less optimism and fewer chances to explore, like a sole wage earner at twenty choosing jobs by pay rather than interest. The misconception is that everyone moves through it the same way; income, culture and discrimination change it.

Culture, and emerging adulthood.

HGD 1505 Culture and Emerging Adulthood

In Asian industrialized countries, emerging adults' self-focused freedom is balanced by obligations to parents, though Japanese young adults now lean toward independence and personally satisfying careers; in Europe emerging adulthood lasts longest. In non-industrialized countries, it exists mainly among the middle-class elite, Arnett writes.

Discrimination, and two cultures.

HGD 1506 Discrimination and Biculturalism

Discrimination can interrupt Black emerging adults' exploration of self and career, and bicultural young people can feel tension between identities; Chinese Canadian young women reported more tension than young men, attributed to differing gender norms. These findings are attributed to their studies and show how context shapes exploration.

Child marriage.

HGD 1507 Child Marriage

Child marriage, before fifteen, truncates exploration and imposes adult roles, like a fourteen-year-old bride leaving school to run a household, with no period of exploration at all. Because child marriage travels with poverty and dropout, its separate effects are hard to isolate.

The payoff: is it a stage?

HGD 1508 Is Emerging Adulthood a Stage?

Arnett proposed emerging adulthood as a new life stage, roughly eighteen to twenty-five, marked by five features. The case rests on real change: credential demands keep young people in school longer, and median ages of marriage and parenthood in industrialized countries sit around thirty, leaving a decade that is neither adolescence nor settled adulthood. Critics raise three questions, and they answer this part's question. Universality: it appears mainly in industrialized countries, and elsewhere only among the middle-class elite. Class: lower-income young people explore less and feel less optimistic. Culture: in Asian industrialized countries self-focus is balanced by obligations, and child marriage removes the period entirely. The misconception is that it is a universal, biologically timed stage. It is better understood as a period many young people in affluent societies now pass through, a real pattern worth studying.

Six entries on the body at its peak, and on the habits, stress and sleep that shape later health.

The physiological peak.

HGD 1509 The Physiological Peak

In the early twenties people are at the peak of physiological development, including muscle strength, reaction time, sensory abilities, and cardiac, lung and immune function. Height stops and sex characteristics complete, while bone density keeps increasing into early adulthood, and genetic predispositions such as hypertension may begin to show.

Early habits, and later health.

HGD 1510 Early Habits and Later Health

Habits set in early adulthood shape later cardiovascular health, and diet and activity protect even people with genetic risk. More education goes with healthier habits, but that is correlational: education, income and access to care travel together, so education alone is not shown to cause better habits.

Activity guidelines.

HGD 1511 Activity Guidelines

US guidelines recommend adults get a hundred fifty minutes of moderate activity a week, or seventy-five minutes of vigorous activity, or an equivalent combination, plus muscle strengthening on two days; brisk walking, gardening and dancing in short bouts add up. The vigorous minutes are an alternative, not an addition, and any activity is better than none.

The physiology of stress.

HGD 1512 Stress Physiology

Stress triggers the fight-or-flight response, releasing two hormones. Adrenaline raises heart rate and blood pressure; chronic activation strains the cardiovascular system and contributes to hypertension and stroke. Cortisol raises blood glucose, adding to the risk of type two diabetes, and suppresses immune function, like a graduate student under months of deadlines who catches every cold. Both are useful in a short emergency; the harm comes from chronic activation. Exam items pair the hormone with its effect. Claims that stress causes cancer rest on weaker human evidence and are not taught as established. The course offers no stress-management advice.

Sleep in early adulthood.

HGD 1513 Sleep in Early Adulthood

Adults are recommended seven to eight hours of sleep a night, yet many young adults sleep poorly, often from stress and anxiety, and sleep debt accumulates: two hours short for seven nights is fourteen hours owed. Poor sleep goes with poorer health, attention and working memory, and risk of depression and alcohol misuse.

Phones, and sleep.

HGD 1514 Phones and Sleep

Heavy phone use goes with worse sleep quality and quantity, but whether screen blue light is the cause is disputed; arousal from messages, lost time and a weakened link between bed and sleep are alternatives. The misconception is that blue light is proven to be the reason; use close to bedtime matters more than total use.

Four entries on health and inequality: childhood income, discrimination, a campus myth, and the limits of one number.

Childhood income, and adult health.

HGD 1515 Childhood SES and Adult Health

Low childhood income affects health across life, through fewer resources, more adverse events, stress and instability, and the effect passes across generations, with the lowest-income quarter of children showing the largest effects later. Health in early adulthood carries the imprint of childhood conditions, not only of current habits.

Discrimination, gender, and health.

HGD 1516 Discrimination, Gender and LGBTQ+ Health

In more than eighteen hundred people followed for a decade from eighteen, more frequent racial discrimination predicted mental-health and substance-use problems, cumulatively. LGBTQ+ emerging adults experience more homelessness and food insecurity, and women, though they live longer on average, face more violence and poverty.

The freshman fifteen.

HGD 1517 The Freshman Fifteen

First-year college students do tend to gain weight, about six in ten of them, but a meta-analysis found a mean gain of about one and a third kilograms, far below fifteen pounds. The misconception is the freshman fifteen; the typical gain is a few pounds.

BMI, and its limits.

HGD 1518 BMI and Its Limits

Obesity in adults is a BMI of thirty or more, but BMI ignores body composition, and the American Medical Association recommends adding waist-based measures. In the obesity paradox, people with higher BMI who develop heart disease sometimes survive longer, found consistently but not universally. BMI does not show whether someone is healthy.

Four entries on substances: the peak years of use, heavy drinking, drug classes, and pathways to disorder.

The peak years of substance use.

HGD 1519 Peak Substance Use

Emerging adulthood is the peak of substance use worldwide and lays groundwork for later misuse, driven by socializing, curiosity, disposable income and coping with stress; young adults use substances to cope more often than they seek counselling. Past-month use is broadly similar by gender and college status, except heavy drinking.

Heavy drinking, and its risks.

HGD 1520 Heavy Drinking and Its Risks

Heavy drinking is most common among male college students, and young adults' substance use raises the risks of mental-health problems, risky sex, violence, injury and crash deaths. In a large registry study, cannabis use disorder was associated with schizophrenia, most strongly in young men, though people vulnerable to psychosis may also be likelier to use cannabis.

Classes of drugs.

HGD 1521 Drug Classes

Psychoactive drugs fall into classes by their main effects. Stimulants, such as cocaine and amphetamines, speed up nervous-system activity. Depressants, such as alcohol, barbiturates and benzodiazepines, slow it down. Opioids, such as heroin, fentanyl and morphine, relieve pain and produce euphoria. Hallucinogens, such as LSD and mescaline, alter perception, with the dissociatives ketamine and PCP grouped with them. Alcohol is often thought a stimulant because people become livelier, but it is a depressant. Some substances, such as cannabis and MDMA, have mixed effects and are classified differently by different sources, so the course assigns them no single class.

Pathways to disorder.

HGD 1522 Pathways to Substance Use Disorder

Some recreational use becomes a substance use disorder, and no single pathway explains it: biological, environmental, psychological and social factors all contribute, from dopamine function and adverse childhood experiences to risk taking and conformity. The course describes risk factors; diagnosis and treatment belong to clinicians.

Four entries on risk and mental health in early adulthood.

Injury and death in early adulthood.

HGD 1523 Injury and Death in Early Adulthood

Despite good health, young adults face elevated deaths from unintentional injury, the leading cause, and from overdose, suicide and homicide. More than forty-eight thousand US firearm deaths occurred in twenty twenty-two, more than half of them suicides, and early exposure to gun violence predicts later involvement in it.

When mental disorders begin.

HGD 1524 When Mental Disorders Begin

A meta-analysis of one hundred ninety-two studies found about forty-eight percent of mental disorders begin before eighteen and about sixty-three percent before twenty-five, with eating disorders and obsessive-compulsive disorder often beginning in adolescence and early adulthood. These are cumulative onset figures, not rising prevalence.

Loneliness, and the pandemic.

HGD 1525 Loneliness and the Pandemic

The COVID pandemic raised depression, anxiety and loneliness across ages, especially among adolescents and young adults, though in one longitudinal study, attributed to Juvonen and colleagues, loneliness among young adults declined after about two years as they adapted to contact through technology.

Suicide risk factors.

HGD 1526 Suicide Risk Factors

Suicide has no single cause, and the CDC groups its risk factors as individual, relationship, community and societal, a grouping that mirrors Bronfenbrenner's systems. Risk is higher among veterans, American Indian and Alaska Native people, rural residents, men, and sexual and gender minorities.

Three entries to close the part, on sexuality, orientation, and coming out in early adulthood.

Sexuality in early adulthood.

HGD 1527 Sexuality in Early Adulthood

Sexuality is one's feelings, beliefs and behaviours about attraction, sexual activity and gender identity; it is self-defined and can change. Sexual activity peaks at about eighteen to twenty-four, though fewer young men were sexually active in twenty eighteen than in two thousand. Asexuality and abstinence are not defects.

Orientation in early adulthood.

HGD 1528 Orientation in Early Adulthood

Nearly a quarter of US adults under thirty identify as LGBTQ+, in Gallup's twenty twenty-five data, and bisexual is the most common LGBTQ+ identity; across thirty countries, about nine percent of adults identify as LGBTQ+. Differences between cohorts partly reflect willingness to identify, not only differences in orientation.

Coming out, and fluidity.

HGD 1529 Coming Out and Sexual Fluidity

Coming-out tasks, recognizing attraction, identifying, a first relationship and disclosure, follow a fairly consistent order, often identification in mid-adolescence and disclosure in emerging adulthood. Women report more sexual fluidity, change in attraction over time, than men.

Look at what you can now do. You can name Arnett's five features: identity exploration, instability, self-focus, feeling in-between, and the age of possibilities. You can state the criticisms of emerging adulthood as a stage: not universal, shaped by class, and balanced or removed by culture. You can match the stress hormones: adrenaline to heart rate and blood pressure, cortisol to blood glucose and a suppressed immune system. You can assign drugs to classes: stimulants speed the nervous system, depressants such as alcohol slow it, opioids relieve pain, hallucinogens alter perception. And you can state when disorders begin: about half before eighteen, nearly two-thirds before twenty-five. Part two opens with sexual health.