emergence of drug expectancies, exposure or initial reactions. Identifying the earliest stage and mechanism for their co-occurrence, following further stages of cross-drug reinforcement and delineating the genetic and environmental underpinnings of these stages will greatly facilitate prevention efforts. Finally, given these associations and overlapping withdrawal symptoms, perhaps even more than with use of alcohol or other drugs, treating tobacco at the same time as cannabis and vice versa may be beneficial to outcomes for both. Empirically based interventions have yet to address and evaluate interventions targeting both substances. Developing outpatient models that do so will likely improve public health by reducing health problems associated with continued use of either substance or their combination.
