Adolescents with externalizing problems tend to come from families where parental monitoring and control is lacking (i.e. under controlled). Externalizing problems are more common among males than females. Risk behaviour refers to behaviours that involve the risk of negative outcomes (e.g. substance use). Problem behaviour refers to behaviour that is viewed as a source of problems (e.g. unprotected sex).

People with externalizing problems often do not experience distress. Externalizing behaviours may be a manifestation of problems with family, friends or school but this need not be the case. It is often not motivated by unhappiness or psychopathology but by desire for excitement and intense experiences.

Driving is the number one source of death in adolescence and emerging adulthood in developed countries. Accidents are especially high in the first few months of driving but fall after having a license for more than a year. This means that inexperience plays a role in the mortality due to driving. However, younger drivers are also more likely to engage in risky driving. This includes driving at excessive speeds (1), following other vehicles too closely (2), violate traffic signs and signals (3), take more risks in lane changing and passing other vehicles (4), allowing too little time to merge (5) and failing to yield to pedestrians (6). They are also more likely to drive under the influence. Next, they are less likely to wear seatbelts.

Parental involvement and monitoring of adolescents’ driving behaviour is important in the early months of driving. Friends’ influence promotes risky driving. Personality characteristics such as sensation seeking and aggressiveness promote risky driving. The optimistic bias (i.e. the belief that one is less likely than others to get into a car crash) is stronger in younger drivers.

Driver education programmes is not very effective in reducing risky driving. Graduated driver licensing (GDL) refers to a programme that allows young people restricted driving privileges when they first receive their license and it gradually increases the privileges if the restrictions are not violated. GDL often consists of three stages:

1. Learning license
   This includes a license where a young person is obtaining driving experience under the supervision of an experienced driver.
2. Restricted license driving
   This refers to a license which allows adolescents to drive without supervision but with tighter restrictions. Restrictions include driving curfews (1), no teenage passengers when no adults are present (2) and zero tolerance for alcohol use (3)
3. Full license
   This refers to a license with all the privileges of a ‘normal’ license.

Substance use is a common form of risk behaviour in adolescence and emerging adulthood. The rate of substance abuse depends on the substance. The majority of people who smoke begin in their early teens. There are ethnic differences in risk behaviour as substance use is greater in Caucasian and Latino populations than in African American and Asian American populations. Substance use rates rise past age 15 through the end of high school.

Binge drinking refers to consuming a large number of alcoholic drinks in one episode (i.e. five or more). This seems to be common for adolescents. Frequent substance use of other drugs is rare. The peak of substance use is in emerging adulthood. The rate of all substance use rises through the late teens in the early 20s before declining in the late 20s.

The propensity and opportunity theory states that people behave defiantly when they have a combination of sufficient propensity (i.e. motivation to behave defiantly) and sufficient opportunity to do so. Emerging adults have a high degree of opportunity for engaging in substance use and other deviant behaviour.

Unstructured socializing refers to young people spending time together with no specific event as the centre of their activity (e.g. driving around). Emerging adults who are highest in unstructured socializing are highest in the use of substances. Substance use may decline in the late 20s due to a sharp decline in unstructured socializing.

There are different reasons to use substances:

1. Experimental substance use
   This refers to trying a substance once or a few times out of curiosity. This is very common in adolescence and emerging adulthood.
2. Social substance use
   This refers to using substances during social activities with friends. Substance use is very common as a group activity in adolescence and emerging adulthood.
3. Medicinal substance use (i.e. self-medication)
   This refers to using substances to relieve an unpleasant emotional state. People who use this tend to use more frequently.
4. Addictive substance use
   This refers to using substances because one is dependent on regular use to feel good physically or psychologically.

People who engage in experimental or social substance use are psychologically healthier than those who engage in medicinal or addictive substance use. Frequent substance use is associated with other problems (e.g. problems in school; withdrawn from peers). Programmes aimed at reducing substance use have been delivered through the school setting (1), family context (2) or a variety of settings (3). Enhancing parental monitoring may be effective. The most successful programmes start in early adolescence and continue on a yearly basis.

Delinquency refers to violations of the law committed by juveniles. The great majority of crimes are committed by young men between the ages of 12 and 25. Adolescents and emerging adults are more likely to be the perpetrators and victims of crimes. Crime rates may be higher in adolescents and emerging adults as they may combine increased independence with increased time with peers and increased orientation toward peers (i.e. unstructured socializing). Peer groups that value and reinforce rule breaking may form – partially due to the rise in sensation seeking - and this may lead to more crime. Crime decreases because the antisocial peer groups break up as emerging adults enter various roles of young adulthood.

Some form of delinquency is common in adolescence. There are two types of delinquency:

1. Life-course persistent delinquency (LCPD)
   This refers to a pattern of problems shown from early childhood and are the result of neuropsychological deficits (e.g. difficult temperament) and being in a high-risk environment (e.g. low-income family). This leads them to often engage in criminal activity and persist into adulthood.
2. Adolescence-limited delinquency (ALD)
   This refers to the absence of criminal activity before and after adolescence. It only occurs during adolescence and emerging adulthood.

In emerging adulthood, life-course persistent delinquents continued to have difficulties (e.g. mental health problems; financial problems) whereas the risk behaviour of adolescence-limited delinquency decreased, although they continued to have more substance use and financial problems than those who did not engage in delinquency (i.e. abstainers).

Delinquency prevention and intervention programmes are typically not effective. This may be because delinquents are not open to change (i.e. they are required to participate) and the prevention programmes take place in adolescence, after a pattern of delinquency has already been established.

Peer contagion refers to the increase in delinquent behaviour that takes place as an unintended consequence of brining adolescents with problems together for an intervention. This occurs because they reinforce each other’s delinquent tendencies and find new partners for delinquent acts.

The multisystemic approach refers to a delinquency prevention strategy that addresses risk factors at several levels (e.g. home; school; neighbourhood) and appears to be effective. It often includes parent training (1), job training (2) and vocational counselling (3). The goal is to direct the energy of delinquents into more socially constructive directions.

According to the Glueck study, the key to delinquency is in the interaction between biological dispositions (i.e. body type; temperament) and family  environments. They were more likely to be from a neglectful or hostile family environment. Job stability and attachment to spouse are the best predictors of staying out of trouble in adulthood.

There are several socialization sources that contribute to delinquency:

• Family structure
  This includes divorced (1), single-parent (2) and step-families (3).
• Family process
  This includes conflict and lack of parental monitoring.
• Parenting styles
  This includes authoritarian, permissive or disengaged parenting.
• Friends’ influence
  This refers to adolescents with a tendency for externalizing problems selecting each other as friends and reinforce this behaviour.
• School
  This includes a school climate that is disorderly and lacks a strong sense of cohesiveness.
• Neighbourhood
  This includes instability and a lack of trust.
• Media
  This includes media depiction of risky behaviours that is rewarded or without negative consequences.
• Legal system
  This includes a focus on punishment rather than rehabilitation.
• Cultural beliefs
  This includes broad rather than narrow socialization.

There are also several individual factors that are predictive of delinquency:

• Gender (i.e. boys).
• Ethnicity (i.e. ethnic minorities).
• Aggressiveness.
• High sensation seeking.
• Cognitive deficits.
• Low impulse control.
• Optimistic bias.

Socialization sources provide a range within which the individual factors may be expressed as externalizing problems. There is cultural variation in how strict the socialization environment is.

A depressed mood refers to an enduring period of sadness without any related symptoms. It is the most common internalizing problem in adolescence with a six-month prevalence of 35%. The most common causes of depressed mood are conflicts with friends or family (1), disappointment or rejection in love (2), and poor performance in school (3).

To receive a diagnosis of major depressive disorder (MDD), at least five of the following symptoms need to be present during a 2-week period and must represent a change from previous functioning:

• Depressed or irritable mood for most of the day, nearly every day.
• Reduced interest or pleasure in all or almost all activities, nearly every day.
• Significant weight loss or gain, or decrease in appetite.
• Insomnia or oversleeping.
• Psychomotor agitation or retardation, observable by others.
• Low energy or fatigue.
• Feelings of worthlessness or inappropriate guilt.
• Diminished ability to think or concentrate.
• Recurrent thoughts of death, recurrent suicidal thoughts.  

At least one symptom must be depressed mood or reduced interest/pleasure. The prevalence of MDD is 3% to 7%. Following the diathesis-stress model, MDD is the result of a predisposition and environmental influences which ‘trigger’ depression. The diathesis for depression may be stronger when the onset of depressive disorder occurs in childhood or adolescence rather than adulthood.

Environmental stressors which can interact with the diathesis to bring about depression include:

• Emotional unavailability of parents.
• High family conflict.
• Economic difficulties.
• Parental divorce.
• Less contact with friends.
• Experiences of rejection.
• Poor peer relationships.

Overall stress is related to depression in adolescence. Depression is more prevalent among boys in childhood but among females throughout adolescence and adulthood. The heightened prevalence of depression among females may be explained by gender roles, with this being emphasized in adolescence. It is also exacerbated by society’s focus on physical appearance (e.g. weight) in females. Girls’ greater body shame led to greater prevalence of depressed mood by mid-adolescence. The higher prevalence among females may also be the result of more stress being experienced by females compared to males. Males are more likely to distract themselves whereas females are more likely to ruminate. They also have a greater focus on interpersonal relationships.

While antidepressants appear to be effective in treating depression, it leads to heightened suicidal thinking and behaviour among some depressed adolescents. There should thus be close monitoring of any adverse effects. Suicidal thinking and behaviour are lower when antidepressants are combined with psychotherapy. Psychotherapy includes group therapy (1), individual therapy (2) and skills training (3). In CBT, the negative attributions are challenged and it aims to change behaviour.

Suicide attempts often occur when depressive symptoms are reducing as people often do not engage in the planning required to commit suicide when the symptoms are at its worst. There are ethnic differences in suicide rates. Females are more likely to attempt suicide but males are more likely to actually succeed.

One major factor for suicide in adolescence is family disruption. Suicide is associated with family life that is chaotic, disorganized, high in conflict and low in warmth. Suicide is often preceded by a period of months in which family problems have worsened. Substance abuse is also common, as well as relationship problems outside of the family. Adolescent suicide takes place not in response to a single stressful or painful event but after a series of difficulties extending over months or years. It is rare for adolescents to show no warning signs of emotional or behavioural problems prior to attempting suicide.

There are several early warning signs of adolescent suicide:

1. Direct suicide threats.
2. A previous suicide attempt.
3. Preoccupation with death in music, art, and personal writing.
4. Loss of a family member, pet, or partner through death, abandonment or breakup.
5. Family disruptions (e.g. serious illness; relocation; divorce; unemployment).
6. Disturbances in sleeping and eating habits and in personal hygiene.
7. Declining grades and lack of interest in school or leisure activities.
8. Drastic changes in behaviour patterns.
9. Pervasive sense of gloom, helplessness, and hopelessness.
10. Withdrawal from family members and friends and feelings of alienation from significant others.
11. Giving away prized possessions and getting their affairs in order.
12. Series of accidents or impulsive, risk-taking behaviour (e.g. alcohol abuse) and disregard for personal safety.

Body dissatisfaction is far more common among girls than among boys. Extreme weight-loss behaviours among adolescent girls (e.g. skipping meals) is related to their mothers’ own extreme weight-loss behaviour.

Anorexia nervosa refers to intentional self-starvation. The prevalence is 1 in 200. About half of the people with anorexia nervosa are also bulimic. To be diagnosed, a person needs to lose at least 15% of their body weight due to restricted food intake. It can result in amenorrhea (i.e. stop of menstruation). There are strong cognitive distortions as they belief that they are too fat.

Bulimia refers to binge eating combined with purging (i.e. intentional vomiting). The prevalence is 3%. Eating disorders are more common in females and especially so for white girls, compared to other ethnic groups. Eating disordered behaviour, without a diagnosis, is more common. People with bulimia often belief that they have a problem and do not view their eating patterns as normal.

Eating disorders are more common in:

• It is more common in cultures that emphasize slimness as part of the female physical ideal.
• It is more common among middle to upper socioeconomic class females.
• It is more common in females in their teens and early 20s.
• It is more common in girls who are exposed to the thin ideal often.

A first step treatment of anorexia is hospitalization to restore the person’s physical functioning. Family therapy may be more effective than individual treatment. CBT may be effective due to the cognitive distortions, although evidence is mixed. About a third of the patients remain chronically ill despite treatment. There is a relapse in 50% of the cases for bulimia and recovery is often slow.

Resilience refers to having good outcomes in spite of serious threats to adaptation and development. There are several protective factors (i.e. resilience factors):

• High intelligence.
• At least one caring adult.
• A healthy school environment (i.e. intellectual balance and positive ethos).
• Religious beliefs and practices.

Emerging adulthood may be a key period for the expression of resilience as emerging adults are able to leave the situation whereas most adolescents cannot.