Adolescent cortical development: a critical period of vulnerability for addiction

Abstract

Cortical growth and remodeling continues from birth through youth and adolescence to stable adult levels changing slowly into senescence. There are critical periods of cortical development when specific experiences drive major synaptic rearrangements and learning that only occur during the critical period. For example, visual cortex is characterized by a critical period of plasticity involved in establishing visual acuity. Adolescence is defined by characteristic behaviors that include high levels of risk taking, exploration, novelty and sensation seeking, social interaction and play behaviors. In addition, adolescence is the final period of development of the adult during which talents, reasoning and complex adult behaviors mature. This maturation of behaviors corresponds with periods of marked changes in neurogenesis, cortical synaptic remodeling, neurotransmitter receptors and transporters, as well as major changes in hormones. Frontal cortical development is later in adolescence and likely contributes to refinement of reasoning, goal and priority setting, impulse control and evaluating long and short term rewards. Adolescent humans have high levels of binge drinking and experimentation with other drugs. This review presents findings supporting adolescence as a critical period of cortical development important for establishing life long adult characteristics that are disrupted by alcohol and drug use.

Fig. 1.

Adolescent alcohol abuse disrupts frontal cortical development and maturation of executive function. This schematic diagram emphasizes the normal focusing of cortical excitation during cerebral tasks that occurs during the transition from adolescent to adult as indicated by the upward narrowing arrow. Frontal cortical remodeling is associated with improved performance at tasks and stabilization of reasoning, impulse control, goal setting, maturation of risk taking, reward sensitivity, motivation, and emotional states. Adult executive functions stabilize after adolescence with a slow decline in senescence. Individuals who have talent (genetics) and training (environment) are most likely to achieve their best abilities at the juncture of adulthood. Individuals who binge drink during adolescence damage and disrupt forebrain cortical development during a critical period of behavioral and cortical maturation. Binge drinking interferes with cortical remodeling as illustrated by the large vertical slightly downward arrow that does not focus. Following adolescence many individuals spontaneously or through therapy reduce their drinking and partially recover executive functions, although they remain lower in ability than those who develop normally. Other individuals remain heavy drinkers continuing to drink. Through the life course many will escalate drinking due to stress, tolerance development, avoidance of negative withdrawal states and other factors that drive them to therapy in their mid-adult years. This model suggests that interventions to reduce adolescent drinking will greatly improve abilities of many individuals and reduce overall lifetime alcoholism and addiction.