Cousijn, Luijten, & Feldstein (2018). Adolescent resilience to addiction: A social plasticity hypothesis.” – Article summary

The prevalence of substance use disorders is highest during adolescence. Many adolescents experience a natural resolution of their substance use by early adulthood without the need of any formal intervention.

Adolescence is characterized by an increase in risk taking and adolescence can be defined as the developmental period between the onset of puberty and the assumption of adult roles and responsibilities. Risk-taking might be adaptive as it may be crucial to adolescents’ successful maturation and movement towards independence. The adolescent brain undergoes rapid changes in how it processes affective and social information. This guides adolescents to choices mainly based on short-term outcomes.

Social attunement refers to a need to adapt and harmonize with the social environment. Adolescents’ capacity to learn from and adapt to their constantly changing social environment is thought to be supported by enhanced socioaffective processing and brain plasticity. This may be both a risk and a protective factor for substance use disorder. This is called the social plasticity hypothesis.

In adolescence, parent input remains important but peer input begins to take primacy. During this period, adolescents are more likely to be in a peer context in which substance use occurs. The proportion of substance-using friends is the best predictor as to whether someone will use substances. The perception of adolescents’ perception of peer substance use is related to their current substance use and their substance use progressions.

The rise in substance use after first experimentation is probably the result of exploration of new social groups, experimentation with new behaviours and reductions in parental monitoring. Most adolescents report a strong, positive effect of their substance use in the social domain. Substance use related accidents (e.g. falling while drunk) affect a large proportion of adolescents and young adults.

Complex cognitive functions (e.g. social cognition) develop throughout adolescence into adulthood. Adolescents primarily prefer short-term outcomes and affective context may drive decision making, especially in early to middle adolescence. The interplay between the changing social environment, heightened emotional arousal and enhanced reward sensitivity leads to more risk-taking and social interactions.

The executive network is involved in cold executive control (i.e. processing events of low emotional salience). It includes the frontoparietal brain areas (e.g. posterior parietal cortex; dorsolateral prefrontal cortex; inferior frontal gyrus; dorsal anterior cingulate cortex). The salience network is the hub for emotion regulation (1), salience attribution (2) and integration of affective information into decision making (3). It includes the ventral anterior cingulate cortex, anterior insula, orbitofrontal cortex and limbic areas (e.g. amygdala). Social cognitive functioning is driven by a network comprised of the medial prefrontal cortex and superior temporal brain areas.

The behavioural changes during adolescence result from widespread changes in structure, connectivity and function among these brain areas. Frontal brain regions involved in social cognition and control mature later than other regions. During adolescence, the functional connectivity during these areas is slowly being enhanced due to the continuation of white matter myelination.

In adolescence, executive control functionality is highly sensitive to social and affective context. This supports the adaptive behavioural flexibility and social attunement to changing social environments. This imbalance may drive risky behaviour at first. The developmentally normative imbalance between social or emotional responsiveness and prefrontal cortex-mediated behavioural control and social cognition may contribute to the cognitive flexibility, social awareness and adaptation of adolescence.

Brain plasticity refers to the dynamic biological capacity of the brain to change in response to the environment. Learning, memory and underlying neural processes play an important role in brain plasticity. Adolescence is characterized by a period of enhanced brain plasticity. Brain plasticity is believed to move from sensory and language development in childhood to learning and complex cognitive functions.

In adolescence, there is a positive memory bias and this is associated with improved learning and enhanced functional connectivity between the hippocampus and the striatum.

During the transition from first-time use to substance dependence, the salience network becomes more attentive and responsive to substance use and substance-use related cues. Poor behavioural control over these motivations, resulting from decreased functioning of the frontoparietal executive network supports further escalation of substance use into substance use disorder. These neural factors predispose adolescents into escalation of substance use disorder.

There are several reasons for the adolescent development of substance-use disorders:

1. Connectivity increases
   The increases in connectivity of the salience and learning networks lead to heightened emotional arousal, reward sensitivity and value of social information. This may elevate the valence and rewarding effects of substance use and related cues.
2. Executive control
   The behavioural control in the context of high affect, intense emotion and highly salient rewards are still developing during adolescence.
3. Social pressure
   There is an increased need to belong and attunement to overt and implicit peer feedback. Meanwhile, the social cognition network is still developing, leading to people using substances to fit in sooner.
4. Enhanced neural plasticity
   There is an enhanced neural plasticity when it comes to associative learning which may drive the formation and strengthening of associations between substance use and rewarding social outcomes.

Adolescents who use alcohol for enhancement (i.e. improve social state) and coping purposes experience more alcohol-related problems than adolescents that drink for social motives. The heightened plasticity during adolescence could lead to brain adaptations in combination with substance use, which leads to the formation of implicit cognitive biases towards substance use (i.e. positive association between substance use and positive outcomes is more easily formed during adolescence).

It is possible that normative improvement of top-down executive control over the salience network increases the capacity to resist substance use in tempting situations. Impulsive decision making eventually halts, in adolescence, and long-term goals become more important. Furthermore, emotional control improves.

As adolescents adopt adult roles, the social benefit of substance use decreases. This devalues the social reinforcing effect of substance use over time. The higher social attunement of adolescents allows them to notice the change in stance toward substance use and this leads to many adolescents maturing out of heavy substance use without the need of a formal intervention. This social attunement in combination with the heightened brain plasticity for associative learning makes it more likely that adolescents will grow out of their substance use.

The early reduction of brain plasticity (e.g. as a result of early onset of puberty) before substance use is socially devalued could hinder de-escalation of substance use. In short, social devaluation of substance use due to high social attunement, integrated with the optimization of behavioural control, during a period where brain plasticity is high leads to adolescent resilience to substance use disorder.