Cigarette smoking and alcohol use as predictors of marijuana use in adolescence and young adulthood: Results from the 2002 and 2003 National Survey on Drug Use and Health

Many studies have been conducted on the associations between licit drug use and marijuana use in adolescence and young adulthood. Very few studies, however, have examined cigarettes and alcohol as separate variables to assess whether there is a difference between these licit drugs and their relationships with marijuana use, and none have focused exclusively on these relationships using a nationally representative sample. The present study investigated the relationships between alcohol, cigarettes, and marijuana use in adolescence and young adulthood using data from the 2002 and 2003 National Surveys on Drug Use and Health. This current study investigated: (1) whether the correlations between alcohol use and marijuana use differ from those between cigarette use and marijuana use, (2) whether each licit drug is a significant, independent predictor of marijuana use after controlling for a comparable measure of the other licit drug, and (3) whether these relationships differ depending on how use is operationally defined. This is the first known study that has assessed multiple levels and definitions of use of alcohol, cigarettes, and marijuana to determine if the licit drugs differ in their associations and predictive values of marijuana use using a nationally representative sample. Overall, cigarette use was a stronger predictor of marijuana use than was alcohol use, particularly when assessing more frequent and higher rates of use; however, it was found that the differences in predictive values of alcohol and cigarette use on marijuana use differed as a function of how use was defined. In addition, cigarette use was a stronger predictor of marijuana use than was smokeless tobacco use, providing evidence that the relationship between cigarettes and marijuana use may be due, in part, to similar modes of ingestion. The methodological and clinical implications of the findings are discussed