A number of study limitations should be addressed in future work. Composite analysis of neuropsychological domains and WM quality may yield more power in assessing areas of neurocognitive vulnerability. In addition, future research should assess neurocognitive functioning in adolescents before they initiate MJ+ALC use to better understand the contribution of premorbid characteristics to substance-related WM changes. Although structural abnormalities appear to persist after sustained abstinence, delineation of the acute and chronic effects of MJ+ALC on brain structure is of interest in future work. The frequent comorbidity of marijuana and alcohol use makes it difficult to examine the separate and combined effects of these substances on brain structure and function. It is possible that the use of one substance can mitigate or potentiate the neurotoxic effects of the other and this mechanism should be further explored in follow-up studies. Finally, protocols that employ higher angular resolution (Frank, 2002) can provide more detailed assessment for exploration of circuitry disruption.
