Marijuana and alcohol are two of the most widely used substances in adolescence. Understanding their role in neurodevelopment may help inform assessment of substance-related cognitive weaknesses and contribute to skill-based training and interventions to optimize cognitive development. The current findings suggest differential influences of white matter development on cognition in MJ+ALC using adolescents than in non-using peers. Neuroadaptation may reflect additive and subtractive responses to substance use that are complicated by competing maturational processes. Additional studies are needed to determine the long-term impact of MJ+ALC use on neurobehavioral functioning, particularly in light of preliminary work indicating a possible reversibility of WM changes with long-term abstinence (Delisi et al., 2006). Longitudinal studies of WM quality in adolescent substance users will also be important for assessing how neurobiological adaptations influence cognitive functioning throughout adolescence and into early adulthood.
