Contribution of alcohol and drug co-use to substance use problems: Data from a nationally-representative sample of US adults who have never been to treatment

Abstract Aims: Combined use of alcohol with drugs elevates risk for problems including injury and driving while intoxicated. We assessed contributions of heavy drinking (5+ drinks for men/4+ for women), drug use (cannabis and other drugs) and simultaneous co-use to DSM-5 alcohol use disorder (AUD) and drug abuse (DA). We expected co-use to increase risk for AUD and DA. Methods: Using population-weighted data from adults in the 2014–2015 National Alcohol Survey who had never been to treatment (N = 3386