Interactive effects of alcohol and cannabis quantities in the prediction of same-day negative consequences among young adults.

Although simultaneous use was associated with more negative consequences than alcohol-only and cannabis-only use, negative consequences on simultaneous use days varied as a function of the interaction between alcohol and cannabis quantities. As findings suggest that using larger amounts of cannabis may attenuate declines in negative consequences associated with lighter drinking, interventions for higher-risk simultaneous use patterns may benefit from a focus on quantities of both alcohol and cannabis.