The latent structure of marijuana and cocaine use disorders: results from the National Longitudinal Alcohol Epidemiologic Survey (NLAES).

To better understand the underlying concepts of substance dependence and abuse, the present study examines the factor structure of DSM-IV lifetime criteria for cannabis and cocaine use disorders. Data for this study were drawn from the National Longitudinal Alcohol Epidemiologic Survey (NLAES), a large nationally representative U.S. sample aged 18 years and older. Exploratory factor analysis (EFA) examined the factor structure for each substance and the factors were related to background covariates using latent variable modeling techniques. Separate analyses were conducted for lifetime marijuana and cocaine users. A two-factor solution was identified for each substance and was similar to DSM-IV abuse and dependence. The factors were highly correlated for both cannabis (r=0.73) and cocaine (r=0.77). Background variables accounted only for a modest amount of factor variance. In conjunction with the findings in alcohol use disorders, these results support the use of consistent criteria across substances in DSM-IV and ICD-10, and suggest that the consistent finding of two correlated factors across substances needs to be better understood.