Externalizing problems consists of several aspects:

• Non-compliance (e.g. ignoring rules).
• Disruptive and aggressive actions.
  
  • Delinquency.
  • Substance use.
  • Fighting.
  • Risky driving.
  • Yelling out.
  • Destroying property.
  • Stealing.

Children with externalizing problems often come from families where parental monitoring and control is lacking (i.e. under-controlled). These problems are more common among males than females. There is a discrepancy between how adults and youth view the behaviour as youth often do not view it as problematic and do not experience distress. The problematic behaviour can be an expression of a desire for excitement (i.e. sensation seeking).

Adolescents are more likely to have accidents when driving due to inexperience and because younger drivers are more likely to engage in risky driving. This includes driving at excessive speeds (1), following other vehicles too close (2), violating traffic signs and signals (3), taking more risks in lane changing and passing other vehicles (4), allowing too little time to merge (5) and failing to yield to pedestrians (6). In addition to this, they are more likely to drive under the influence and less likely to wear seatbelts.

Risky driving is influenced by parental involvement (1), parental monitoring (2), friends’ influence (3), sensation seeking (4), aggressiveness (5) and the optimistic bias (6). The optimistic bias refers to the belief that one is less likely than others to get into a car crash. This belief is stronger in younger drivers. The probability of an accident during adolescence increases depending on how many peers are in the car.

Almost all risk behaviour increases during adolescence. There are differences in risk behaviour (e.g. drinking) depending on whether one looks at onset, frequency, culture or gender.

Substance use is a common form of risk behaviour in adolescence and emerging adulthood. The rate of substance abuse depends on the substance. The rate of all substance use rises through the late teens in the early 20s before declining in the late 20s with the peak of substance use being in emerging adulthood. There are different reasons to use substances:

• Experimental substance use (i.e. curiosity; common in adolescence).
• Social substance use (i.e. using substances during social activities).
• Medicinal substance use (i.e. self-medication; relieve unpleasant emotional state).
• Addictive substance use (i.e. dependency; addiction).

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 spending time together with no specific event as the centre of activity (e.g. driving around). Substance use may be especially high during unstructured socializing due to the lack of activity and sensation seeking. Substance use may decline in the late 20s due to a decline in unstructured socializing.

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. Initiation and maintenance of substance use patterns is predicted by friends and peer group member use of substances and by previous use.

In peer groups and among best friends, there are similar drinking behaviours. This homogeneity may be the result of selection processes and socialization processes, meaning that there is a transactional model between substance use and peer substance use.

Drinking typically takes place in a social context and is influenced by social interactions and social norms. Other people’s drinking behaviour influences one’s drink choice (1), speed (2) and quantity (3). Imitation is important for the development of drinking (i.e. modelling). Exposure to a drinking model leads to more imitation in drinking behaviour and this also holds on a sipping level.

This mainly occurs in a same-sex dyad. Men do not imitate the model more than women although they do consume more alcohol. There is a genetic susceptibility to heavy drinking and people with this susceptibility consume more alcohol when paired with a heavy drinking peer.

Peer relationships moderate the association between marital problems and child adjustment. The quality of friendship is important for this, especially in adolescence. A low friendship quality is a risk factor for aggravating the effect of interpersonal conflict on anxiety for both boys and girls. For aggression, this only holds for boys. High and normal quality friendships do not differ in their effects, meaning that low friendship quality may have a stronger effect. Peer relationships can be both a risk and protective factor.

A successful adolescent has a positive, well-organized interaction with their friends. However, the topic of this interaction can be deviance. When a friendship focuses on deviance, the friendship predicts escalations in antisocial behaviour (i.e. deviancy training). When antisocial teenagers interact closely with each other and spend their time discussing deviance (e.g. substance abuse; breaking the law), they tend to engage in more problem behaviour. Friendships closely bonded over deviant values may thus more heavily influence problem behaviours. It is important to be careful about creating opportunities for antisocial youth to form close friendships with each other (e.g. group treatment for juvenile delinquents) as this may exacerbate rather than treat the problems (i.e. peer contagion). Peer socialization processes support growth in problem behaviour.

Longitudinal studies self-report studies often fail to take into account the context and real-life interactions and often lead to small effects. The processes of influence (e.g. in the case of substance use) can be measured by using real-time observations of interactions (i.e. micro causality). Experimental studies could also be used to manipulate the influence of peers, though the ecological validity is debated.

Delinquency refers to violation of the law committed by juveniles. The vast majority of crimes are committed by young males between the ages of 12 and 25. Adolescents and emerging adults are more likely to be both the perpetrator and victim of a crime. Delinquency may rise due to unstructured socialization. Crime may decrease in late emerging adulthood because antisocial peer groups break up as they enter various roles of young adulthood.

Moffitt distinguishes two types of delinquents:

1. Adolescence-limited delinquents (ALDs)
   This refers to delinquents who engage in criminal acts in adolescence and emerging adulthood but there is no evidence of problems before or after adolescence and emerging adulthood. The origins of this delinquency is in social processes. It is relatively common.
2. Life-course persistent delinquents (LCDPs)
   This refers to delinquents who show a history of related problems prior to adolescence and continue problematic behaviour after adolescence. The origin of this delinquency is in neurodevelopmental processes. There is an interaction between neurodevelopmental weaknesses and family adversity risk factors. The neurodevelopmental vulnerability is exacerbated by environmental risk factors. It is uncommon but it is persistent and pathological (i.e. 10-15% of the delinquents).

The accumulation of risk and missed opportunities can lead to a disordered personality and antisocial behaviour. A life-course persistent delinquent is more likely to experience family adversity (e.g. low SES). While the risk behaviour of adolescence-limited delinquency decreases, they continued to have more substance use and financial problems than those who did not engage in delinquency (i.e. abstainer). Moffit’s theory is supported by longitudinal studies. However, when using reviews, the evidence is not always clear as the length of criminal career is not always predicted by different risk factors which are believed to be central to the pathway.

It is possible that AL men are able to profit from opportunities for desistence of antisocial behaviour whereas this is not possible for LCP men due to their childhood which led to antisocial patterns and personalities. However, all men’s offending declines with age and adult-onset antisocial behaviour seems unlikely to exit due to their history of problematic childhood or conduct problems.

Abstainers may exist due to a lack of maturity gap (1), barriers that may prevent them from learning about delinquency (2) and personal characteristics unappealing to other teens that bar abstainers from risk-taking teen groups (e.g. high conscientiousness). Abstainers are typically later in puberty (1), withdrawn (2), shy (3), socially anxious (4), methodical (5), conscientious (6), rational thinkers (7) and good at coping (8). One abstainer group is characterized by low popularity and one which is characterized by high honesty.

According to the Glueck study, the key to delinquency is the interaction between biological dispositions (i.e. body type; temperament) and family environments. Job stability and attachment to spouse are the best predictors of staying out of trouble in adulthood.

There are several factors that are related to externalizing problems:

1. Individual characteristics
   1. Gender (i.e. boys).
   2. Ethnicity (i.e. ethnic minorities).
   3. Temperament (i.e. aggressiveness).
   4. Sensation seeking / impulse control.
   5. School achievement.
   6. Risk perceptions (i.e. low risk perception)
   7. Cognitive deficits.
   8. Optimistic bias.
2. Socialization influences
   
   1. Family structure (i.e. divorced; single-parent; step-families; low SES).
   2. Family process (i.e. conflict; lack of parental monitoring).
   3. Parenting style (i.e. authoritarian; permissive; disengaged).
   4. Friends and peers.
   5. School (e.g. school climate).
   6. Neighbourhood (e.g. safety).
   7. Media (e.g. exposure to violence without negative consequences).
   8. Cultural beliefs.
   1. Legal system (i.e. focus on punishment rather than rehabilitation).

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.

Aggressiveness refers to any behaviour that is aimed at harming others. It includes not controlling hostile impulses. There are two forms of aggression;

1. Instrumental aggression
   This refers to aggression which is motivated by non-aggressive reasons and aims to achieve a goal (e.g. steal to get money, not to harm).
2. Hostile aggression
   This refers to aggression where the major goal is to inflict harm.

There are different developmental trajectories of physical aggression. One trajectory group with high physical aggression is characterized by the children coming from low income families (1), mothers not having completed high school (2), ineffective or hostile parenting (3) and the children being boys (4). There are three general trajectories:

1. High stable (16.6%)
   This refers to children who show a lot of physical aggression and this is stable from toddlerhood to adolescence.
2. Moderate desisters (52.2%)
   This refers to children who show moderate levels of physical aggression in toddlerhood but this slowly decreases over time to adolescence.
3. Low desisters (31.1%)
   This refers to children who show low levels of physical aggression in toddlerhood and this decreases even more over time to adolescence.

Childhood aggressiveness at age 8 predicts adult indicators of aggression at age 30. Sensation seeking refers to a personality trait which includes the seeking of varied, novel, complex and intense sensations and experiences and the willingness to take physical, social, legal and financial risk for the sake of such experiences. This has a genetic and biological basis and is associated with aggression.