Age of onset and alcohol and cannabis use disorders among Mexican American young adults: Robust substance-specific effects of early use as a risk factor.

We investigated the substance-specific and cross-substance risk associated with early onset (before age 15) of drunkenness and cannabis use in the subsequent development of alcohol (AUD) and cannabis use disorder (CUD) in Mexican American young adults. Survival analyses employed Cox proportional hazards models for AUD and CUD, separately. In cross-risk analyses, we modeled estimates for those participants reporting lifetime use of both substances. Early onset of drunkenness and early onset of cannabis use were associated with shorter time to AUD and CUD, respectively, even after accounting for psychiatric disorders. While there were no cross-risk associations, adjusting for psychiatric disorders and early onset cannabis use attenuated the association of early drunkenness with AUD.