"While covariates differed between equations, early regular use of tobacco and alcohol emerged as the 2 factors most consistently associated with later illicit drug use and abuse/dependence. While early regular alcohol use did not emerge as a significant independent predictor of alcohol dependence, this finding should be treated with considerable caution, as our study did not provide an optimal strategy for assessing the effects of early alcohol use."
Lynskey, Michael T., PhD, et al. Escalation of Drug Use in Early-Onset Cannabis Users vs Co-twin Controls. Journal of the American Medical Association, Vol. 289 No. 4, January 22/29, 2003.