well as poor white matter integrity. Understanding risk and protective factors for alcohol and marijuana use in adolescents and the consequences of sustained use are the subject of ongoing study and programming efforts. The frequency of polysubstance use underscores the need for research examining the interactive effects of substances on brain structure, particularly given that the pharmacodynamics of one drug may mitigate or potentiate the neurotoxic components of another. Further, integration of genetic, hormonal, neural, and behavioral characteristics via cross-modal analyses is needed in future research to identify biomarkers for substance problems and targets for treatment. In addition, longitudinal neurobehavioral studies will be important for assessing and differentiating the enduring and potentially reversible effects of alcohol and other drug use during adolescence.
