Overlapping alcohol and marijuana use and unsafe driving among US high school seniors: 1976-2011

BACKGROUND. This analysis investigated associations between self-reported overlapping alcohol and marijuana use (OAM) and tickets/warnings and accidents among high school seniors. METHODS. From 1976-2011, annual surveys of nationally representative cross-sectional samples of 12th grade students in the coterminous US collected data via in-school questionnaires. Students self-reported past 12-month frequency of (a) using alcohol and marijuana concurrently, and (b) tickets/accidents (responses did not indicate if overlapping/concurrent use directly preceded unsafe driving). Data from 71,594 students were used to examine (a) if the likelihood of tickets/accidents varied by level of substance use involvement (no alcohol or marijuana use; alcohol only; marijuana only or both alcohol and marijuana, but no reported OAM; OAM); (b) whether the number of tickets/accidents was associated with degree of OAM; and (c) the stability of observed associations over time. RESULTS. The likelihood of unsafe driving was significantly higher with each reported level of substance use involvement, and the risks of both tickets/warnings and accidents following either alcohol or marijuana use was associated with the level of reported past 12-month OAM. Associations were generally stable over time and held after controlling for miles driven, substance use frequency, and other factors known to associate with driving under the influence. CONCLUSIONS. Efforts to effectively educate US high school students—especially substance users—on the increased risks associated with combined alcohol and marijuana use are needed in ways that are believable and effective. This increased awareness may be especially needed given recent state policy movement toward legalization of adult recreational marijuana use.