Week 6 Glossary Terms:

Adolescence

(Paris, Ricardo, & Rymond, 2019)
Adolescence is often defined as the period that begins with puberty and ends with the shift to adulthood. The commonly accepted beginning age for this period of development is age 12. When it ends is harder to pin down. When does adulthood truly begin? Are we an adult at 18 years of age? 20? Even older?

Adolescence physical development has evolved historically, with evidence indicating that this stage is lengthening as individuals start puberty earlier and shift to adulthood later than in the past. Puberty today begins, on average, at age 10–11 years for girls and 11–12 years for boys. This average age has decreased gradually over time since the 19th century by 3–4 months per decade, which has been attributed to a range of factors including better nutrition, obesity, increased father absence, and other factors (L. D. Steinberg, 2013).

Completion of formal education, financial independence from parents, marriage, and parenthood mark the end of adolescence and the beginning of adulthood, and all of these changes happen, on average, later now than in the past.

Physical Development

Physical Growth

The adolescent growth spurt is a rapid increase in an individual’s height and weight during puberty resulting from the simultaneous release of growth hormones, thyroid hormones, and androgens. Males experience their growth spurt about two years later than females. The accelerated growth in various body parts happens at different times, but for all adolescents it has a fairly regular sequence. The first places to grow are the head, hands, and feet, followed by the limbs, and later the upper body and shoulders. This non-uniform growth is one reason why an adolescent body may seem out of proportion. During puberty, bones become harder and more brittle.

Before puberty, there are nearly no differences between males and females in the distribution of fat and muscle. During puberty, males grow muscle much faster than females, and females experience a higher increase in body fat. An adolescent’s heart and lungs increase in both size and capacity during puberty; these changes contribute to increased strength and ability for exercise.

Brain Growth

(Lally & Valentine-French, 2022)
Brain growth continues into the early twenties. The development of the frontal lobe, in particular, is important during this stage. Adolescents often engage in increased risk-taking behaviors and experience heightened emotions during puberty; this may be due to the fact that the frontal lobes of their brains—which are responsible for judgment, impulse control, and planning—are still maturing until early adulthood (Casey et al., 2005).

The brain undergoes dramatic changes during adolescence. Although it does not get larger, it matures by becoming more interconnected and specialized (Giedd, 2015). The myelination and development of connections between neurons continues. This results in an increase in the white matter of the brain, and allows the adolescent to make significant improvements in their thinking and processing skills. Different brain areas become myelinated at different times. For example, the brain’s language areas undergo myelination during the first 13 years. Completed insulation of the axons merges these language skills but makes it more difficult to learn a second language. With greater myelination, however, comes diminished plasticity as a myelin coating inhibits the growth of new connections (Dobbs, 2011).

Even as the connections between neurons are strengthened, synaptic pruning occurs more than it did during childhood as the brain adapts to changes in the environment. This synaptic pruning causes the gray matter of the brain, or the cortex, to become thinner but more efficient (Dobbs, 2011). The corpus callosum, which connects the two hemispheres, continues to thicken, allowing for stronger connections between brain areas. Additionally, the hippocampus becomes more strongly connected to the frontal lobes, allowing for greater integration of memory and experiences into our decision-making.

(Zimmerman & Snow, 2012)
The limbic system, which regulates emotion and reward, is linked to the hormonal changes that occur at puberty. The limbic system is also related to novelty seeking and a shift toward interacting with peers. In contrast, the prefrontal cortex, which is involved in the control of impulses, organization, planning, and making good decisions does not fully develop until the middle twenties. According to Giedd (2015), the significant aspect of the later developing prefrontal cortex and early development of the limbic system is the mismatch in timing between the two (Giedd, 2015). The approximately ten years that separates the development of these two brain areas can result in risky behavior, poor decision-making, and weak emotional control for the adolescent. When puberty begins earlier, this mismatch extends even further.

Teenagers often take more risks than adults and, according to research, it is because they weigh risks and rewards differently than adults do (Dobbs, 2011). For adolescents, the brain’s sensitivity to the neurotransmitter dopamine peaks, and dopamine is involved in reward circuits so the possible rewards exceed the risks. Adolescents respond especially strongly to social rewards during activities, and they prefer the company of others their same age. In addiction to dopamine, the adolescent brain is affected by oxytocin, which facilitates bonding and makes social connections more rewarding. With both dopamine and oxytocin engaged, it is no wonder that adolescents seek friends and excitement in their lives that could end up actually harming them.

Because of all the changes that occur in the adolescent brain, the chances for abnormal development can occur, including mental illness. In fact, 50 percent of mental illness occurs by the age 14 and 75 percent occurs by age 24 (Giedd, 2015). Additionally, during this period of development the adolescent brain is especially exposed to damage from drug exposure. For example, repeated exposure to marijuana can affect cellular activity in the endocannabinoid system. Consequently, adolescents are more sensitive to the effects of repeated marijuana exposure (Weir, 2018).

However, researchers have also focused on the highly adaptive qualities of the adolescent brain, which allow the adolescent to move away from the family towards the outside world (Dobbs, 2011; Giedd, 2015). Novelty seeking and risk taking can generate positive outcomes including meeting new people and seeking out new situations. Separating from the family and moving into new relationships and different experiences are actually quite adaptive for Society (Zimmerman & Snow, 2012).

The physical growth and the changes of puberty mark the beginning of adolescence (Brown & Larson, 2009). For both boys and girls, these changes include a growth spurt in height, growth of pubic and underarm hair, and skin changes (for example, pimples). Hormones drive these pubescent changes, particularly the increase in testosterone for boys and estrogen for girls (Lansford, 2019).

Physical Changes in Adolescence

Adolescence begins with puberty, a developmental period in which hormonal changes cause rapid physical alterations in the body, resulting in sexual maturity. Although the timing varies to some degree across cultures, the average age range for reaching puberty is between 9 and 14 years for girls and between 10 and 17 years for boys (Marshall & Tanner, 1986). This period of physical development of the adolescent age 9–13 is divided into two phases (Stangor, 2019).

The first phase of puberty begins when the pituitary gland begins to stimulate the production of the male sex hormone testosterone in boys and the female sex hormones estrogen and progesterone in girls. The release of these sex hormones triggers the development of the primary sex characteristics, the sex organs concerned with reproduction. It also involves height increases from 20–25 percent. Puberty is second to the prenatal period in terms of rapid growth as the long bones stretch to their final, adult size. Girls grow 2–8 inches (5–20 centimeters) taller, while boys grow 4–12 inches (10–30 centimeters) taller.

Secondary sexual characteristics are physical changes not directly linked to reproduction but signal sexual maturity. The growth spurt for girls usually occurs earlier than that for boys, with some boys continuing to grow into their 20s. For males this includes broader shoulders, a larger Adam’s apple, and a lower voice as the larynx grows. Boys typically begin to grow facial hair between ages 14 and 16, which becomes darker and coarser, and hair growth occurs in the pubic area, under the arms, and on the face.

For females, the enlargement of breasts is usually the first sign of puberty and, on average, occurs between ages 10 and 12 (Marshall & Tanner, 1986). Girl’s hips broaden and pubic and underarm hair develops and becomes darker and coarser. Both boys and girls experience a rapid growth spurt during this stage. Males and females may begin shaving during this time period as well as showing signs of acne on their faces and bodies.

Acne is an unpleasant consequence of the hormonal changes in puberty. Acne is defined as pimples on the skin due to overactive sebaceous (oil-producing) glands (Dolgin, 2011). These glands develop at a greater speed than the skin ducts that discharge the oil. Consequently, the ducts can become blocked with dead skin and acne will develop. According to the University of California at Los Angeles Medical Center (2000), approximately 85 percent of adolescents develop acne, and boys develop acne more than girls because of greater levels of testosterone in their systems (Dolgin, 2011). Hormones that are responsible for sexual development can also cause acne on the teenage skin (Lally & Valentine-French, 2022).

A major milestone in puberty for girls is menarche, the first menstrual period, typically experienced at around 12–13 years of age (Anderson et al., 2003). The age of menarche varies greatly and is determined by genetics, as well as by diet and lifestyle, since a certain amount of body fat is needed to attain menarche. Girls who are very slim, engage in demanding athletic activities, or are malnourished may begin to menstruate later. Even after menstruation begins, girls whose level of body fat drops below the critical level may stop having their periods. The sequence of events for puberty is more predictable than the age at which they occur. Some girls may begin to grow pubic hair at age 10 but not attain menarche until age 15 (Stangor, 2012).

Male Anatomy

(Lally & Valentine-French, 2022)
Males have both internal and external genitalia that are responsible for procreation and sexual intercourse. Males produce their sperm on a cycle different from the female's ovulation cycle; the male sperm production cycle is constantly producing millions of sperm daily. The male sex organs are the penis and the testicles, the latter of which produce semen and sperm. The semen and sperm, as a result of sexual intercourse, can fertilize an ovum in the female's body. The fertilized ovum (zygote) develops into a fetus, which is later born as a child.

Female Anatomy

Female external genitalia is collectively known as the vulva, which includes the mons veneris, labia majora, labia minora, clitoris, vaginal opening, and urethral opening. Female internal reproductive organs consist of the vagina, uterus, fallopian tubes, and ovaries. The uterus hosts the developing fetus, produces vaginal and uterine secretions, and passes the male's sperm through to the fallopian tubes while the ovaries release the eggs. A female is born with all her eggs already produced. The vagina is attached to the uterus through the cervix, while the The uterus is attached to the ovaries via the fallopian tubes. Females have a monthly reproductive cycle. At certain intervals the ovaries release an egg, which passes through the fallopian tube into the uterus. If, in this transit, it meets with sperm, the sperm might penetrate and merge with the egg, fertilizing it. If not fertilized, the egg and the tissue that was lining the uterus is flushed out of the system through menstruation (around every 28 days).

Effects of Puberty on Development

The age of puberty is getting younger for children throughout the world. A century ago the average age of a girl’s first period in the United States and Europe was 16, while today it is around 13. Because there is no clear sign of puberty for boys, it is harder to determine if boys are maturing earlier, too. In addition to better nutrition, less positive reasons associated with early puberty for girls include increased stress, obesity, and endocrine disrupting.

Because rates of physical development vary so widely among teenagers, puberty can be a source of pride or embarrassment. Girls and boys who develop more slowly than others may feel self-conscious about their lack of physical development; some research has found that negative feelings are particularly a problem for late maturing boys, who are at a higher risk for depression and conflict with parents (Graber et al., 1997) and more likely to be bullied (Pollack & Shuster, 2000). Additionally, problems are more likely to occur when the child is among the first in their peer group to develop. Because the preadolescent time is one of not wanting to appear different, early developing children stand out among their peer group and gravitate toward those who are older (Weir, 2016).

Early maturing boys tend to be physically stronger, taller, and more athletic than their later maturing peers; this can contribute to differences in popularity, which can influence the teenager’s confidence. Some studies show that boys who mature earlier tend to be more popular and independent but are also at a greater risk for substance abuse and early sexual activity (Flannery et al., 1993; Kaltiala-Heino et al., 2001). Early maturing girls may face increased teasing and sexual harassment related to their developing bodies, which can contribute to self-consciousness and place them at a higher risk for anxiety, depression, substance abuse, and eating disorders (Ge et al., 2001; Graber et al., 1997; Striegel-Moore & Cachelin, 1999).

The Brain and Sex

(Lally & Valentine-French, 2022)
The brain is the structure that translates the nerve impulses from the skin into pleasurable sensations. It controls nerves and muscles used during sexual behavior. The brain regulates the release of hormones, which are believed to be the physiological origin of sexual desire. The cerebral cortex, which is the outer layer of the brain that allows for thinking and reasoning, is believed to be the origin of sexual thoughts and fantasies. Beneath the cortex is the limbic system, which consists of the amygdala, hippocampus, cingulate gyrus, and septal area. These structures are where emotions and feelings are believed to originate, and are important for sexual behavior.

The hypothalamus is the most important part of the brain for sexual functioning. This is the small area at the base of the brain consisting of several groups of nerve-cell bodies that receives input from the limbic system. Studies with lab animals have shown that destruction of certain areas of the hypothalamus cause complete elimination of sexual behavior. One of the reasons for the importance of the hypothalamus is that it controls the pituitary gland, which secretes hormones that control the other glands of the body.

Hormones

Several important sexual hormones are secreted by the pituitary gland. Oxytocin, also known as the hormone of love, is released during sexual intercourse when an orgasm is achieved.

Oxytocin is also released in females when they give birth or are breast-feeding; it is believed that oxytocin is involved with maintaining close relationships. Both prolactin and oxytocin stimulate milk production in females. Follicle-stimulating hormone (FSH) is responsible for ovulation in females by triggering egg maturity. It also stimulates sperm production in males. Luteinizing hormone (LH) triggers the release of a mature egg in females during the process of Ovulation.

In males, testosterone appears to be a major contributing factor to sexual motivation. Vasopressin is involved in the male arousal phase, and the increase of vasopressin during erectile response may be directly associated with increased motivation to engage in sexual behavior.

The relationship between hormones and female sexual motivation is not as well understood, largely due to the overemphasis on male sexuality in Western research. Estrogen and progesterone typically regulate motivation to engage in sexual behavior for females, with estrogen increases motivation and progesterone decreases it. The levels of these hormones rise and fall throughout a woman's menstrual cycle. Research suggests that testosterone, oxytocin, and vasopressin are also implicated in female sexual motivation in similar ways as in males, but more research is needed to understand these relationships.

Sleep Health

According to the National Sleep Foundation (NSF), in 2016 adolescents need about 8–10 hours of sleep each night to function best. The most recent Sleep in America poll in 2024 indicated that most adolescents between sixth and twelfth grade were not getting the recommended amount of sleep. For the older adolescents, only about 1 in 10 (9 percent) get the recommended amount of sleep, and they are more likely to experience negative consequences the following day. These include feeling too tired or sleepy, being grumpy, falling asleep in school, having a depressed mood, and drinking caffeinated beverages (NSF, 2016). Additionally, they are at risk for substance abuse, car crashes, poor academic performance, obesity, and a weakened immune system (Weintraub, 2016).

Why don’t adolescents get adequate sleep? In addition to known environmental and social factors, including work, study, media, technology, and socializing, the adolescent brain is also a factor. As adolescents go through puberty, their circadian rhythms change and push back their sleep time until later in the evening (Weintraub, 2016). This biological change not only keeps adolescents awake at night, it makes it difficult for them to get up in the morning. When they are awake too early, their brains do not function properly. Impairments are noted in attention, behavior, and academic achievement, while increases in tardiness and absenteeism are also demonstrated. Psychologists and other professionals have been advocating for later school times, and they have produced research demonstrating better student outcomes for later start times. More middle and high schools have changed their start times to better reflect sleep research.

Eating: Healthy Habits Equal Healthy Lives

(Zimmerman & Snow, 2012)
After puberty, the rate of physical growth slows down. Girls stop growing taller around age 16, while boys continue to grow taller until ages 18–20. One of the psychological and emotional changes that take place during this life stage includes the desire for independence as adolescents develop individual identities apart from their families. As teenagers make more of their dietary decisions, parents, caregivers, and authority figures should guide them toward appropriate, nutritious choices.

Some adolescents don’t have all the food necessary for proper development and may be food insecure. Most people have access to fresh water in all except the most severe situations; the need for food is the most fundamental and important human need. More than 1 in 10 U.S. households contain people who live without enough nourishing food and this lack of proper nourishment has significant effects on their abilities to lead lives that will allow them to develop to their fullest potential (World Hunger Education Service, n.d.).

When people are hungry, their motivation to attain food completely changes their behavior. Hungry people become inactive and apathetic to save energy and then become completely obsessed with food. Ancel Keys and his colleagues (Keys et al., 1950) found that volunteers who were placed on severely reduced-calorie diets lost all interest in sex and social activities, becoming preoccupied with food. According to Maslow, meeting one’s basic needs is vital for proper growth and development.

Abraham Maslow’s Hierarchy of Needs

(Boundless, 2016)
Maslow’s theory is based on a simple premise: human beings have needs that are hierarchically ranked. There are some needs that are basic to all human beings, and in their absence, nothing else matters. We are ruled by these needs until they are satisfied. After we satisfy our basic needs, they no longer serve as motivators and we can begin to satisfy higher-order needs.

Maslow organized human needs into a pyramid that includes (from lowest-level to highest-level) physiological, safety, love and belonging, esteem, and self-actualization. According to Maslow, one must satisfy lower-level needs before addressing needs that occur higher in the pyramid. For example, if someone is starving, it is not likely that he will spend a lot of time wondering whether other people think he is a good person. Instead, all of his energies are geared toward finding something to eat.

Weight Management

(Stangor, 2012)
Forming good eating habits and engaging in fitness or exercise programs will help maintain a healthy weight and develop long-lasting habits. Research says that the best way to control weight is to eat less (consume fewer calories) and exercise (burn more calories). To maintain a healthy weight, restricting your diet alone is difficult and can be significantly improved when it is accompanied by increased physical activity.

The energy (calorie) requirements for preteens differ according to gender, growth, and activity level. For ages 9–13, girls should consume about 1,400–2,200 calories per day and boys should consume 1,600–2,600 calories per day. Physically active preteens who regularly participate in sports or exercise need to eat a greater number of calories to account for increased energy.

People who exercise regularly, and in particular those who combine exercise with dieting, are less likely to be obese (Borer, 2008). Exercise not only improves our physical health, but also our overall mental health by reducing stress and improving feelings of well-being. Exercise also increases cardiovascular capacity, reduces blood pressure, and helps improve diabetes, joint flexibility, and muscle strength (Fletcher et al., 1996). For long lasting change, it’s important to plan healthy meals, limit snacking, and schedule exercise into our daily lives.

Diet Extremes: Obesity to Starvation

In this section, we’ll learn about the two ends of the spectrum (or extremes) of nutritional outcomes.

Obesity

(Zimmerman & Snow, 2012)

Children need adequate caloric intake for growth, and it is important not to impose highly restrictive diets. However, exceeding caloric requirements on a regular basis can lead to childhood obesity, which has become a major problem in North America. Nearly 1 of 3 US children and adolescents are overweight or obese. 

There are a number of reasons behind the problem of obesity, including:

• Larger portion sizes

• Limited access to healthy foods

• Increased access to fast foods and vending machines

• Lack of breastfeeding support

• Decline of physical education programs in schools

• Little physical activity and a sedentary routine

• Media messages encouraging the eating of unhealthy foods

Obesity has a significant effect on self-esteem, energy, and activity level. Even more importantly, it is a major risk factor for a number of diseases later in life, including cardiovascular disease, type 2 diabetes, stroke, hypertension, and certain cancers.

A percentile for body mass index (BMI) specific to age and sex is used to determine if a child is overweight or obese. If a child gains weight inappropriate to growth, parents and caregivers should limit energy-dense, unhealthy snack foods. In addition, it is highly beneficial to increase a child’s physical activity and limit sedentary activities, such as watching television, playing video games, or surfing the Internet. Programs to address childhood obesity can include behavior modification, exercise counseling, psychological support or therapy, familycounseling, and family meal-planning advice. (Zimmerman & Snow, 2012)

Eating Disorders

Although eating disorders can occur in children and adults, they frequently appear during the teen years or young adulthood (National Institute of Mental Health, 2016). Eating disorders affect both genders, although rates among women are two and a half times greater than among men. Similar to women who have eating disorders, men also have a distorted sense of body image, including body dysmorphia or an unhealthy concern with becoming more muscular (Hudson et al., 2007; Wade et al., 2011). 

Risk Factors for Eating Disorders

Researchers are finding that eating disorders are caused by a complex interaction of genetic, biological, behavioral, psychological, and social factors  (National Institute of Mental Health, 2016). Eating disorders appear to run in families, and researchers are working to identify DNA variations that are linked to the increased risk of developing eating disorders. Researchers have also found differences in patterns of brain activity in women with eating disorders in comparison with healthy women. The main criteria for the most common eating disorders are described in the Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition (DSM-5) and listed the table below (American Psychiatric Association, 2013): DSM-5 Eating Disorders (Lally & Valentine-French, 2022).

Health Consequences of Eating Disorders

For those suffering from anorexia, health consequences include an abnormally slow heart rate and low blood pressure, which increases the risk for heart failure. Additionally, there is a reduction in bone density (osteoporosis), muscle loss and weakness, severe dehydration, fainting, exhaustion, and overall weakness. Individuals with this disorder may die from complications associated with anorexia nervosa, which has the highest mortality rate of any psychiatric disorder.

The binge and purging cycle of bulimia can affect the digestives system and lead to electrolyte and chemical imbalances that can affect the heart and other major organs. Frequent vomiting can cause inflammation and possible rupture of the esophagus, as well as tooth decay and staining from stomach acids. Lastly, binge-eating disorder results in similar health risks to obesity, including high blood pressure, high cholesterol levels, heart disease, type 2 diabetes, and gallbladder disease (National Eating Disorders Association, 2016).

Eating Disorders Treatment

The bases of treatment for eating disorders include adequate nutrition and stopping destructive behaviors, such as purging (forced vomiting). Treatment plans are made to fit individual needs and include medical care, nutritional counseling, medications (such as antidepressants), and individual, group, and/or family psychotherapy (National Institute of Mental Health, 2016).

Drug and Substance Abuse

(Lally & Valentine-French, 2022)

Drug use and the possibility of abuse and addiction primarily appear as physical problems. However, the effects of these substances are not only physical. They also have long lasting consequences on cognitive development as well as effect social emotional development in a variety of ways. In the next section we’ll learn about what drugs are, the different kinds of drugs, and what the effects are of each.

Drug Experimentation

Drug use is, in part, the result of socialization. Adolescents may try drugs when their friends convince them to, and these decisions are based on social norms about the risks and benefits of various drugs. Despite the fact that young people have experimented with cigarettes, alcohol, and other dangerous drugs for many generations, it would be better if they did not. All recreational drug use is associated with at least some risks, and those who begin using drugs earlier are also more likely to use more dangerous drugs. They may develop an addiction or substance abuse problem later on (Stangor, 2012).

What Are Drugs?

A psychoactive drug is a chemical that changes our states of consciousness, and particularly our perceptions and moods. These drugs are commonly found in everyday foods and drinks including chocolate, coffee, and soft drinks, as well as in alcohol and in over-the-counter drugs, such as aspirin, Tylenol, and cold and cough medication. Psychoactive drugs are also frequently prescribed as sleeping pills, tranquilizers, and antianxiety medications, and they may be taken, illegally, for recreational purposes. The four primary classes of psychoactive drugs are stimulants, depressants, opioids, and hallucinogens.

Stimulants

A stimulant is a psychoactive drug that operates by blocking the reuptake of dopamine, norepinephrine, and serotonin in the synapses of the central nervous system (CNS). Because more of these neurotransmitters remain active in the brain, the result is an increase in the activity of the sympathetic division of the autonomic nervous system (ANS). Effects of stimulants include increased heart and breathing rates, pupil dilation, and increases in blood sugar accompanied by decreases in appetite. For these reasons, stimulants are frequently used to help people stay awake and to control weight.

Used with restraint, some stimulants may increase alertness, but used in an irresponsible fashion they can quickly create dependency. A major problem is the crash that results when the drug loses its strength and the activity of the neurotransmitters returns to normal. The withdrawal from stimulants can create severe depression and lead to an intense desire to repeat the high.

Depressants

In contrast to stimulants, which work to increase neural activity, a depressant slows down consciousness. A depressant is a psychoactive drug that reduces the activity of the CNS.

Depressants are widely used as prescription medicines as anticonvulsants, to relieve pain, and lower heart rate and respiration. . The outcome of depressant use (similar to the effects of sleep) is a reduction in the transmission of impulses from the lower brain to the cortex (Csáky & Barnes, 1984). 

Opioids

Opioids are chemicals that increase activity in opioid receptor neurons in the brain and in the digestive system, producing euphoria, analgesia, slower breathing, and constipation. Their chemical framework is similar to the endorphins, the neurotransmitters that serve as the body’s natural pain reducers. Natural opioids are derived from the opium poppy, which is widespread in Eurasia, but they can also be created artificially.

Hallucinogens

The drugs that produce the most severe alteration of consciousness are the hallucinogens, psychoactive drugs that alter sensation and perception and may create hallucinations. Hallucinogens are also known as psychedelics. Drugs in this class include lysergic acid diethylamide (LSD, or Acid), mescaline, and phencyclidine (PCP), as well as a number of natural plants including cannabis (marijuana), peyote, and psilocybin. The hallucinogens may produce noticeable changes in perception through one or more of the senses. The precise effects a user experiences are a function not only of the drug itself but of the user’s preexisting mental state and expectations of the drug experience. The hallucinations that may be experienced when taking these drugs are strongly different from everyday experience and frequently are more similar to dreams than to everyday consciousness.

Substance Abuse

Many drugs create tolerance, which is an increase in the dose required to produce the same effect, which makes it necessary for the user to increase the dose or the number of times per day that the drug is taken. As the use of the drug increases, the user may develop a dependence, or a need to use a drug or other substance regularly. Dependence can be psychological, meaning the drug is desired and has become part of the everyday life of the user, but no serious physical effects result if the drug is not obtained; or physical, meaning serious physical and mental effects appear when the drug is removed. Cigarette smokers who try to quit, for example, experience physical withdrawal symptoms, such as becoming tired and grouchy.  Extreme psychological cravings can occur as well. This includes needing  a cigarette in particular situations, such as after a meal or when they are with friends. Users may wish to stop using the drug, but when they reduce their dose they experience withdrawal. Negative experiences that accompany reducing or stopping drug use include physical pain and other symptoms. When the user powerfully craves the drug and is driven to seek it out, over and over again, no matter what the physical, social, financial, and legal cost, we say that they have developed an addiction to the drug.

It is a common belief that addiction is a consuming, powerful force, and that withdrawal from drugs is always a painful experience. But the reality is more complex and in many cases less severe. For one, even drugs that we do not generally think of as being addictive, such as caffeine, nicotine, and alcohol, can be very difficult to quit using. On the other hand, drugs that are normally associated with addiction, including amphetamines, cocaine, and heroin, do not immediately create addiction in their users. Even for a highly addictive drug like cocaine, only about 15 percent of users become addicted (Berridge & Robinson, 2003; Wagner & Anthony, 2002).  Furthermore, the rate of addiction is lower for those who are taking drugs for medical reasons than for those who are using drugs recreationally. Patients who have become physically dependent on morphine given during the course of medical treatment for a painful injury or disease are able to be rapidly weaned off the drug after treatment without becoming addicts (The Open University of Hong Kong, n.d.).

People have used, and often abused, psychoactive drugs for thousands of years. Perhaps this should not be surprising, because many people find using drugs to be enjoyable. Even when we know the potential costs of using drugs, we may engage in them anyway because the pleasures of using the drugs are occurring in the moment, whereas the potential costs are abstract and occur in the future (Stangor, 2012).

Cognitive Development

Brain Growth

The human brain is not fully developed by the time a person reaches puberty. Between the ages of 10 and 25, the brain undergoes changes that have important effects on behavior. The brain reaches 90 percent of its adult size by the time a person is 6–7 years of age. The brain does not grow in size much during adolescence. However, the creases in the brain continue to become more complex until the late teens. The biggest changes in the folds of the brain during this time occur in the parts of the cortex that process cognitive and emotional information.

(Lazzara, 2020)

Up until puberty, brain cells continue to grow in the frontal region. Some of the most developmentally significant changes in the brain occur in the prefrontal cortex, which is involved in decision-making, cognitive control, and other higher cognitive functions. During adolescence, myelination and synaptic pruning in the prefrontal cortex increases, improving the efficiency of information processing, and neural connections between the prefrontal cortex and other regions of the brain are strengthened. However, this growth takes time and can be  irregular.

The limbic system develops years ahead of the prefrontal cortex. Development in the limbic system plays an important role in determining rewards and punishments and processing emotional experience and social information. Pubertal hormones target the amygdala directly and powerful sensations become compelling (Romeo, 2017). Brain scans confirm that cognitive control—revealed by fMRI studies—is not fully developed until adulthood because the prefrontal cortex is limited in connections and engagement (Hartley & Somerville, 2015). Recall that this area is responsible for judgment, impulse control, and planning, and is still maturing into early adulthood (Casey et al., 2005).

Additionally, changes in both the levels of the neurotransmitters dopamine and serotonin in the limbic system make adolescents more emotional and responsive to rewards and stress. Dopamine is a neurotransmitter in the brain associated with pleasure and adapting to the environment during decision-making. During adolescence, dopamine levels in the limbic system increase and input of dopamine to the prefrontal cortex increases. The increased dopamine activity in adolescence may have effects on adolescent risk-taking and vulnerability to boredom. Serotonin is involved in the regulation of mood and behavior. It affects the brain in a different way. Known as the calming chemical, serotonin eases tension and stress. Serotonin also puts a brake on the excitement and sometimes carelessness that dopamine can produce. If there is a defect in the serotonin processing in the brain, impulsive or violent behavior can result.

When the overall brain chemical system is working well, these chemicals seem to balance out extreme behaviors. But when stress, arousal, or sensations become powerful, the adolescent brain is flooded with impulses that overwhelm the prefrontal cortex, and as a result, adolescents engage in increased risk-taking behaviors and emotional outbursts, possibly because the frontal lobes of their brains are still developing.

Later in adolescence, the brain’s cognitive control centers in the prefrontal cortex develop, increasing adolescents’ self-regulation and future orientation. The difference in timing of the development of these different regions of the brain contributes to more risk-taking during middle adolescence because adolescents are motivated to seek thrills that sometimes come from risky behavior, such as careless driving, smoking, or drinking. They have not yet developed the cognitive control to resist urges or focus equally on the potential risks (L. D. Steinberg, 2013).  One of the world’s leading experts on adolescent development, Laurence Steinberg, compares this to engaging a powerful engine before the braking system is in place. The result is that adolescents are more inclined to risky behaviors than are children or adults.

Many who have read the research on the teenage brain come to quick conclusions about adolescents as irrational and wild. However, adolescents are actually making choices influenced by a very different set of chemical influences than their adult equivalents; a reward system that can drown out warning signals about risk. Adolescent decisions are not always defined by impulsivity because of lack of brakes, but because of planned and enjoyable pressure to the accelerator. It is helpful to put all of these brain processes in a developmental context. Young people need to somewhat enjoy the thrill of risk-taking in order to complete the incredibly difficult task of growing up.

Cognitive Changes in the Brain

(Paris, Ricardo, & Rymond, 2019)

Early in adolescence, changes in dopamine, a chemical in the brain that is a neurotransmitter

and produces feelings of pleasure, can contribute to increases in adolescents’ sensation-seeking and reward motivation. During adolescence, people tend to do whatever activities produce the most dopamine without fully considering the consequences of such actions. Later in adolescence, the prefrontal cortex, the area of the brain responsible for outcomes, forming judgments, controlling impulses and emotions, also continues to develop (Goldberg, 2001). The difference in timing of the development of these different regions of the brain contributes to more risk taking during middle adolescence because adolescents are motivated to seek thrills (L. Steinberg, 2008).  The result is that adolescents are inclined to risky behaviors more often than children or adults.

Although the most rapid cognitive changes occur during childhood, the brain continues to develop throughout adolescence, and even into the twenties (Weinberger et al., 2005). The brain continues to form new neural connections and becomes faster and more efficient because it prunes, or casts off, unused neurons and connections (Blakemore, 2008), and produces myelin (the fatty tissue that forms around axons and neurons) which helps speed transmissions between different regions of the brain (Paus et al., 1999). 

This time of rapid cognitive growth for teenagers, making them more aware of their potential and capabilities, causes a great amount of disequilibrium for them. Theorists have researched cognitive changes and functions and have formed theories based on this developmental period. (Paris, Ricardo, Raymond, et al., 2019)

(Lansford, 2019)

Jean Piaget: Formal Operational Stage of Cognitive Development

Cognition refers to thinking and memory processes, and cognitive development refers to long-term changes in these processes. One of the most widely known perspectives about cognitive development is the cognitive stage theory of a Swiss psychologist named Jean Piaget. Piaget created and studied an account of how children and youth gradually become able to think logically and scientifically.

Piaget was a psychological constructivist. In his view, learning was proceeded by the interplay of assimilation (adjusting new experiences to fit prior concepts) and accommodation (adjusting concepts to fit new experiences). The to-and-fro of these two processes leads not only to short-term learning, but also to long-term developmental change. The long-term developments are really the main focus of Piaget’s cognitive theory.

As you might remember, Piaget proposed that cognition developed through distinct stages from birth through the end of adolescence. By stages he meant a sequence of thinking patterns with four key features:

1. They always happen in the same order.

2. No stage is ever skipped.

3. Each stage is a significant alteration of the stage before it.

4. Each later stage incorporated the earlier stages into itself.

This is basically a staircase model of development. Piaget proposed four major stages of cognitive development: (1) sensorimotor intelligence, (2) preoperational thinking, (3) concrete operational thinking, and (4) formal operational thinking. Each stage is correlated with an age period of childhood, but only approximately. Formal operational thinking appears in adolescence (Seifert et al., 2009).

During the formal operational stage, adolescents are able to understand abstract principles. They are no longer limited by what can be directly seen or heard, and are able to contemplate such constructs as beauty, love, freedom, and morality. Additionally, while younger children solve problems through trial and error, adolescents demonstrate hypothetical-deductive reasoning, which is developing hypotheses based on what might logically occur. They are able to think about all the possibilities in a situation before and then test them systematically, because they are able to engage in true scientific thinking (Crain, 2005).

Does Everyone Reach Formal Operations?

According to Piaget, most people attain some degree of formal operational thinking, but use formal operations primarily in the areas of their strongest interest (Crain, 2005). In fact, most adults do not regularly demonstrate formal operational thought. A possible explanation is that an individual’s thinking has not been sufficiently challenged to demonstrate formal operational thought in all areas.

Adolescent Egocentrism

Once adolescents can understand abstract thoughts, they enter a world of hypothetical possibilities and demonstrate egocentrism, a heightened self-focus. The egocentricity comes from attributing unlimited power to their own thoughts (Crain, 2005). Piaget believed it was not until adolescents took on adult roles that they would be able to learn the limits to their own thoughts.

Psychosocial Development

Moral Reasoning

(Lazzara, 2020)

As adolescents become increasingly independent, they also develop more nuanced thinking about morality, or what is right or wrong. We all make moral judgments on a daily basis. As adolescents’ cognitive, emotional, and social development continue to mature, their understanding of morality expands and their behavior becomes more closely associated with their values and beliefs. Therefore, moral development describes the progression of these guiding principles and is demonstrated by the ability to apply these guidelines in daily life. Understanding moral development is important in this stage where individuals make many important decisions and gain more legal responsibility.

Lawrence Kohlberg argued that moral development moves through a series of stages, and reasoning about morality becomes increasingly complex (somewhat in line with increasing cognitive skills, as per Piaget’s stages of cognitive development) (Kohlberg, 1984). As children develop intellectually, they pass through three stages of moral thinking: the preconventional level, the conventional level, and the postconventional level. In middle childhood to early adolescence, the child begins to care about how situational outcomes impact others and wants to please and be accepted (conventional morality). At this developmental phase, people are able to value the good that can be derived from holding to social norms in the form of laws or less formalized rules. Adolescents begin to employ abstract reasoning to justify behaviors from adolescence and beyond. Moral behavior is based on self-chosen ethical principles that are generally comprehensive and universal, such as justice, dignity, and equality, which is postconventional morality.

Influences on Moral Development

Adolescents are open to their culture, to the models they see at home, in school, and in the mass media. These observations influence moral reasoning and moral behavior. When children are younger, their family, culture, and religion greatly influence their moral decision-making. During the early adolescent period, peers have a much greater influence. Peer pressure can be a powerful influence because friends play a more significant role in teenagers’ lives. Furthermore, the new ability to think abstractly enables youth to recognize that rules are simply created by others. As a result, teenagers begin to question the absolute authority of parents, schools, government, and other traditional institutions (Vera-Estay et al., 2015). By late adolescence, most teenagers are less rebellious as they have begun to establish their own identity, their own belief system, and their own place in the world.

Unfortunately, some adolescents have life experiences that may interfere with their moral development. Traumatic experiences may cause them to view the world as unjust and unfair. Additionally, social learning also impacts moral development. Adolescents may have observed the adults in their lives making decisions that disregarded the rights and welfare of others, leading these youth to develop beliefs and values that are contrary to the rest of society. That being said, adults have opportunities to support moral development by modeling the moral character that we want to see in our children. Parents are particularly important because they are generally the original source of moral guidance. Authoritative parenting facilitates children’s moral growth better than other parenting styles. One of the most influential things a parent can do is encourage the right kind of peer relations. While parents may find this process of moral development difficult or challenging, it is important to remember that this developmental step is essential to their children’s well-being and ultimate success in life.

Identity Development

Identity development is a stage in the adolescent life cycle. For most, the search for identity begins in the adolescent years. During these years, adolescents are more open to trying different behaviors and appearances to discover who they are. In an attempt to find their identity and discover who they are, adolescents are likely to cycle through a number of identities to find one that suits them best. Developing and maintaining identity (in adolescent years) is difficult due to factors such as family life, environment, and social status. Empirical studies suggest that this process might be more accurately described as identity development, rather than formation, but confirms a normative process of change in both content and structure of one’s thoughts about the self.

Self-Concept

Two main aspects of identity development are self-concept and self-esteem. The idea of self-concept is known as the ability of a person to have opinions and beliefs that are defined confidently, consistently, and with stability. Early in adolescence, cognitive developments result in greater self-awareness, greater awareness of others and their thoughts and judgments, the ability to think about abstract, future possibilities, and the ability to consider multiple possibilities at once. As a result, adolescents experience a significant shift from the simple, concrete, and global self-descriptions typical of young children; as children, they define themselves by physical attributes whereas adolescents define themselves based on their values, thoughts, and opinions.

Adolescents can imagine multiple possible selves that they could become and their choices’ long-term possibilities and consequences. Exploring these possibilities may result in abrupt changes in self-presentation as the adolescent chooses or rejects qualities and behaviors, trying to guide the actual self toward the ideal self (who the adolescent wishes to be) and away from the feared self (who the adolescent does not want to be). For many, these distinctions are distressing, but they also appear to motivate achievement through behavior consistent with the ideal and distinct from the feared possible selves.

Further distinctions in self-concept, called differentiation, occur as the adolescent recognizes the contextual influences on their own behavior and the perceptions of others, and begin to qualify their qualities when asked to describe themselves. Differentiation appears fully developed by the middle of adolescence. Peaking in the 7th–9th grades, the personality qualities adolescents use to describe themselves refer to specific contexts, and therefore may contradict one another. The recognition of conflicting content in the self-concept is a common source of distress in these years, but this distress may benefit adolescents by encouraging structural development.

Self-Esteem

Another aspect of identity formation is self-esteem. Self-esteem is defined as one’s thoughts and feelings about one’s self-concept and identity. Most theories on self-esteem state that there is a grand desire, across all genders and ages, to maintain, protect, and enhance their self-esteem. Contrary to popular belief, there is no empirical evidence for a significant drop in self-esteem over the course of adolescence. Barometric self-esteem fluctuates rapidly and can cause severe distress and anxiety, but basic self-esteem remains highly stable across adolescence. The validity of global self-esteem scales has been questioned, and many suggest that more specific scales might reveal more about the adolescent experience. Girls are most likely to enjoy high self-esteem when engaged in supportive relationships with friends, the most important function of friendship to them is having someone who can provide social and moral support. When they fail to win friends’ approval or can’t find someone with whom to share common activities and common interests, girls suffer from low self-esteem.

In contrast, boys are more concerned with establishing and asserting their independence and defining their relation to authority. As such, they are more likely to derive high self-esteem from their ability to successfully influence their friends. On the other hand, the lack of romantic ability, for example, failure to win or maintain the affection of the opposite or same-sex (depending on sexual orientation), is the major contributor to low self-esteem in adolescent boys.

Adolescents continue to refine their sense of self as they relate to others. Erik Erikson referred to life’s fifth psychosocial task as one of identity versus role confusion when adolescents must work through the difficulties of finding one’s own identity. Individuals are influenced by how they resolved all of the previous childhood psychosocial crises and this adolescent stage is a bridge between the past and the future, between childhood and adulthood. Thus, in Erikson’s view, an adolescent’s main questions are “Who am I?” and “Who do I want to be?” Identity formation was highlighted as the primary indicator of successful development during adolescence (in contrast to role confusion, which would be an indicator of not successfully meeting the task of adolescence). This crisis is resolved positively with identity achievement and the gain of fidelity (ability to be faithful) as a new virtue when adolescents have reconsidered the goals and values of their parents and culture. Some adolescents adopt the values and roles that their parents expect for them. Other teenagers develop identities that oppose their parents but associate with a peer group. This is common as peer relationships become a central focus in adolescents’ lives.

Along the way, most adolescents try on many different selves to see which ones fit. They explore various roles and ideas, set goals, and attempt to discover their adult selves. Adolescents who are successful at this stage have a strong sense of identity and are able to remain true to their beliefs and values in the face of problems and other people’s perspectives. When adolescents are apathetic, do not consciously search for identity, or are pressured to conform to their parents’ ideas for the future, they may develop a weak sense of self and experience role confusion. They will be unsure of their identity and confused about the future. Teenagers who struggle to adopt a positive role will likely struggle to find themselves as adults.

Identity Formation: Who am I?

Expanding on Erikson’s theory,  Marcia  described identity formation during adolescence as involving decision points and commitments concerning ideologies (for example, religion and politics) and occupations (Marcia, 1966). Foreclosure occurs when an individual commits to an identity without exploring options. Identity confusion or diffusion occurs when adolescents neither explore nor commit to any identities. Moratorium is a state in which adolescents are actively exploring options but have not yet made commitments. As mentioned earlier, individuals who have explored different options, discovered their purpose, and have made identity commitments are in a state of identity achievement.

Developmental psychologists have researched several different areas of identity development and some of the main areas include:

• Religious identity: The religious views of teenagers are often similar to those of their families (Kim-Spoon et al., 2012). Most teenagers may question specific customs, practices, or ideas in the faith of their parents, but few completely reject the religion of their families.

• Political identity: An adolescent’s political identity is also influenced by their parents’ political beliefs. A new trend in the 21st century is a decrease in party association among adults. Many adults do not align themselves with either the democratic or republican party and their teenage children reflect their parents’ lack of party association. Although adolescents tend to be more liberal than their elders, especially on social issues (Taylor, 2014), like other aspects of identity formation, adolescents’ interest in politics is predicted by their parents’ involvement and by current events (Stattin et al., 2017). 

• Vocational identity: While adolescents in earlier generations visualized themselves as working in a particular job, and often worked as an apprentice or part-time in such occupations as teenagers, this is rarely the case today. Vocational identity takes longer to develop, as most of today’s occupations require specific skills and knowledge that will require additional education or are acquired on the job itself. In addition, many of the jobs held by teenagers are not in occupations that most teenagers will seek as adults.

• Ethnic identity: Ethnic identity refers to how people come to terms with who they are based on their ethnic or racial ancestry. According to the United States Census more than 40 percent of Americans under the age of 18 are from ethnic minorities (U.S. Census Bureau, 2012). For many ethnic minority teenagers, discovering one’s ethnic identity is an important part of identity formation. Phinney proposed a model of ethnic identity development that included stages of unexplored ethnic identity, ethnic identity search, and achieved ethnic identity (Phinney, 1989).

• Gender identity: A person’s sex, as determined by their biology, does not always correspond with their gender. Sex refers to the biological differences between males and females, such as the genitalia and genetic differences. Gender refers to the socially constructed characteristics of women and men, such as norms, roles, and relationships between groups of women and men. Many adolescents use their analytic and hypothetical thinking to question traditional gender roles and expression. If their genetically assigned sex does not line up with their gender identity, they may refer to themselves as transgender, non-binary, or gender-nonconforming.

• Gender identity refers to a person’s self-perception as male, female, both, genderqueer, or neither. Cisgender is an umbrella term used to describe people whose sense of personal identity and gender corresponds with their birth sex, while transgender is a term used to describe people whose sense of personal identity does not correspond with their birth sex. Gender expression, or how one demonstrates gender (based on traditional gender role norms related to clothing, behavior, and interactions) can be feminine, masculine, androgynous, or somewhere along a spectrum.

• Fluidity and uncertainty regarding sex and gender are especially common during early adolescence when hormones increase and fluctuate creating difficulty of self-acceptance and identity achievement (Reisner et al., 2016). Gender identity, like vocational identity, is becoming an increasingly extended task as attitudes and norms regarding gender keep changing. The roles appropriate for males and females are evolving and some adolescents may foreclose on a gender identity as a way of dealing with this uncertainty by adopting more stereotypic male or female roles (Sinclair & Carlsson, 2013). Those that identify as transgender may face even bigger challenges. 

Relationships

The Parent-Child Relationship

(Paris, Ricardo, & Rymond, 2019)

The relationship with parents may be a mitigating factor of the negative influence by peers. Communicating family rules and parental style have been inversely associated to substance, alcohol, and tobacco consumption during adolescence. This influence is essential for adolescents’ development up to adulthood. Communication between parents and adolescents emerges as a protective factor for alcohol, tobacco, and substance use (Newman et al., 2008).

Sen observed that family meals could lead to creating a closer relation between parents and adolescents, by strengthening a positive relationship and avoiding certain risk behaviors, such as substance use amongst girls and alcohol consumption, physical violence, and robberies amongst boys (Sen et al., 2015). These differences between genders may be due to a greater importance that girls attribute to family activities but they do not reveal that boys are uninterested in them, only that the relation between genders may differ. Huebner and Howell confirmed that parental monitoring and communication with parents protected adolescents of both genders from being involved in risk behaviors (Huebner & Howell, 2003).

Parental monitoring can be defined as parents’ knowledge about their children’s activities, who they hang out with and what they do. It has been associated to protection of various risk behaviors throughout adolescence, such as substance use or sexual behaviors. The greater the parental monitoring, the lower the adolescents’ involvement in risk behavior. It may vary according to age, gender, or ethnicity and it generally decreases with age (Westling et al., 2008). 

Relationships with Peers and Peer Groups

Peer Relationships

(Tomé et al., 2012)

Peers also serve as an important source of social support and companionship during adolescence. As children become adolescents, they usually begin spending more time with their friends and less time with their families, and these peer interactions are increasingly unsupervised by adults. The level of influence that others can have over an adolescent makes these relationships particularly important in their personal development. Adolescents with positive relationships are happier and better adjusted than those who are socially isolated or have conflicting relationships.

Adolescents’ notions of friendship increasingly focus on intimate exchanges of thoughts and feelings, which are important to forming relationships ; these high quality friendships may enhance a child’s development regardless of the particular characteristics of those friends.

The peer group may serve as a model and influence behaviors and attitudes (Glaser et al., 2010). Social learning theory suggests that it is not necessary for adolescents to observe a given behavior and adopt it; it is sufficient to perceive that the peer group accepts it in order to be able to select similar behaviors (Petraitis et al., 1995).

(Tomé et al., 2012)
Peers can serve both positive and negative functions during adolescence. Relationships with others are valuable opportunities for adolescents to practice their social and conflict resolution skills. But negative peer pressure can lead adolescents to make risky decisions or engage in more unsafe behavior than they would alone or in the presence of their family. One of the most widely studied aspects of adolescent peer influence is known as deviant peer contagion (Dishion & Tipsord, 2011), which is the process by which peers encourage problem behavior by laughing or showing other signs of approval that then increase the likelihood of future problem behavior.

(Boundless, 2016)
Peers may strongly determine preference in the way of dressing, speaking, using prohibited substances, sexual behavior, adopting and accepting violence, adopting criminal and antisocial behaviors, and many other areas of the adolescent’s life (Padilla‐Walker & Bean, 2009; Tomé et al., 2008).  

An example of this is that the main motives for alcohol consumption given by adolescents are related to social events, which usually take place in the company of friends, namely: drinking makes holidays more fun, it facilitates approaching others, it helps relaxing or facilitates sharing experiences and feelings (Kuntsche et al., 2005). Also, copying risk behaviors may be greater when consumption begins in the context of a social event (Larsen et al., 2010).

On the other hand, having friends allows sharing experiences and feelings and learning how to solve conflicts. Not having friends, on the other hand, leads to social isolation and limited social contacts, as there are fewer opportunities to develop new relations and social interaction skills.

Friendship is also positively associated with psychological well-being (Ueno, 2004). Stronger friendships may provide adolescents with an appropriate environment to development in a healthy way and to achieve good academic results. Adolescents with complementary friendships mention high levels of feelings of belonging in school; harmony and feelings of belonging have positive effects in academic results (Vaquera & Kao, 2008). 

School is a setting where interpersonal relations are promoted, which are important for adolescents’ personal and social development (Ruini et al., 2009). It is responsible for the transmission of behavioral norms and standards and it represents an essential role in the adolescent’s socialization process. The school is able to gather different communities and promote self-esteem and a harmonious development between adolescents, which makes it a privileged space for meetings and interactions (Baptista et al., 2008).

Adolescents spend a great part of their time at school, which also makes it a privileged context for involvement in or protection from risk behaviors confirmed that adolescents who like school were those that more often were part of a peer group without involvement in risk behaviors (Piko & Kovács, 2010). Those that mentioned they did not have any friends reported that they liked school less and those in conflict with their peers had more negative health outcomes (Camacho et al., 2010).

Despite the positive influence of the peer group during adolescence, the higher the adolescent’s autonomy from the peer group, the higher their resilience against its influence. This resilience seems to increase with age, which may mean that it is associated with adolescent maturity; and girls emerge in several studies as more resilient than boys (Sumter et al., 2009). 

Another factor that may be found in the influence of the peer group is the type of friendship which adolescents maintain with their group. If friends are close they have a greater influence on the other’s behaviors (Glaser et al., 2010). When the friendship is perceived as reciprocal and of quality, it exercises greater influence (Mercken et al., 2010). 

Another factor which has been identified as a possible way of decreasing peer influence is assertive refusal. Adolescents that are able to maintain an assertive refusal are at less risk to the group’s influence (Glaser et al., 2010).

These are only some variables identified as possible factors decreasing peer influence. (Tomé et al., 2012)

Peers in Groups

During adolescence, it is common to have friends of the opposite sex much more than in childhood.

Childhood friend groups as they evolve from primarily single-sex to mixed-sex. Teenagers within a peer group tend to be similar to one another in behavior and attitudes, which has been explained as a function of homophily, that is, adolescents who are similar to one another choose to spend time together. Adolescents who spend time together also shape each other’s behavior.

Crowds are an emerging level of peer relationships in adolescence. In contrast to friendships, which are reciprocal pair relationships and cliques (groups of individuals who interact frequently), crowds are characterized by shared reputations or images (who people think they are). Crowds refer to different collections of people, like the athletes or the environmentalists. In a way, they are kind of like clothing brands that label the people associated with different crowds. 

Behavioral and Psychological Adjustment

Aggression and Antisocial Behavior

(Learning & Overstreet, 2017)

Several major theories of the development of antisocial behavior treat adolescence as an important period. Patterson’s  early versus late starter model of the development of aggressive and antisocial behavior distinguishes youths whose antisocial behavior begins during childhood (early starters) versus adolescence (late starters) (Patterson, 1982). According to the theory, early starters are at greater risk for long-term antisocial behavior that extends into adulthood than are late starters. Late starters who become antisocial during adolescence are theorized to experience poor parental monitoring and supervision, aspects of parenting that become more important during adolescence. Poor monitoring and lack of supervision contribute to increasing involvement with deviant peers, which in turn promotes the adolescent's own antisocial behavior. Late starters cease from antisocial behavior when changes in the environment make other options more appealing.

Similarly, Moffitt’s life-course persistent versus adolescent-limited model distinguishes between antisocial behavior that begins in childhood versus adolescence (Moffitt, 1993). Moffitt regards adolescent-limited antisocial behavior as resulting from a maturity gap between adolescents’ dependence on and control by adults and their desire to demonstrate their freedom from adult constraint. However, as they continue to develop, and adult roles and privileges become available to them, there are fewer incentives to engage in antisocial behavior, leading to resistance in these antisocial behaviors.

Anxiety and Depression

Developmental models of anxiety and depression also treat adolescence as an important period, especially in terms of the emergence of gender differences in prevalence rates that persist through adulthood (Rudolph, 2009). Starting in early adolescence, when compared with males, females have rates of anxiety that are about twice as high and rates of depression that are 1.5 to 3 times as high (American Psychiatric Association, 2013). Although the rates vary across specific anxiety and depression diagnoses, rates for some disorders are noticeably higher in adolescence than in childhood or adulthood. For example, prevalence rates for specific phobias are about 5 percent in children and 3–5 percent in adults but 16 percent in adolescents. Additionally, some adolescents sink into a major depression, a deep sadness and hopelessness that interrupts all normal, regular activities. Causes include many factors, such as genetics and early childhood experiences that precede adolescence, but puberty may push sensitive children, especially girls, into despair.

During puberty, the rate of major depression more than doubles to an estimated 15 percent, affecting about 1 in 5 girls and 1 in 10 boys. The gender difference occurs for biological and cultural reasons (Uddin et al., 2010). Anxiety and depression are particularly concerning because suicide is one of the leading causes of death during adolescence. Some adolescents experience suicidal ideation (distressing thoughts about killing oneself) which becomes most common at about age 15 (Berger, 2019) and can lead to parasuicide, also called attempted suicide or failed suicide. Suicidal ideation and parasuicide should be taken seriously and serve as a warning that emotions can  be overwhelming.

Developmental models focus on interpersonal contexts in both childhood and adolescence that foster depression and anxiety. Family diffculties, such as abuse and parental psychopathology during childhood, sets the stage for social and behavioral problems during adolescence. Adolescents with such problems generate stress in their relationships (for example, by resolving conflict poorly and constantly seeking reassurance) and select more maladaptive social contexts. These processes are intensified for girls compared to boys because girls have more relationship-oriented goals related to intimacy and social approval, leaving them more exposed to disturbances in these relationships. Anxiety and depression then intensify problems in social relationships, contributing to the stability of anxiety and depression over time.

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