Marijuana and other substance use among male and female underage drinkers who drive after drinking and ride with those who drive after drinking.

The study sought to describe the occurrence of adolescent driving after drinking (DD) and riding with a driver who had been drinking (RWDD) and associations with substance use for both males and females. As part of screening for a randomized controlled trial, we surveyed 16-20year olds (N=3418) recruited from an emergency department (ED) and analyzed data from those reporting past-year alcohol consumption (n=2150, 58% females). DD was reported by 22% of females and 28% of males and RWDD was reported by 39% of females and 38% of males, also in the past year. In regression models, risky alcohol use and past-year marijuana use were associated with increased odds of DD and RWDD for females and males. Marijuana use was a strong predictor, with odds increased by 2.3 and 1.7 times for DD among females and males respectively and 1.4 times for RWDD for females and males. Prescription drug misuse was also associated with RWDD for females and for both males' and females' reported DD. The findings highlight the alarming rate of DD and RWDD among both males and females and suggest ED-based injury prevention efforts consider such risky road behavior as well as consider their substance use. Future research might also further examine the effects of driving under influence of substances, particularly marijuana, and the negative synergistic effects of co-ingestion prior to driving.