The stepping-stone hypothesis--marijuana, heroin, and causality.
D000428:Alcohol Drinking; D006556:Heroin Dependence / Q000209:etiology*; D006801:Humans; D007604:Juvenile Delinquency / Q000523:psychology; D008297:Male; D002189:Marijuana Abuse / Q000150:complications*; D012306:Risk; D012907:Smoking; D012917:Social Adjustment; D012931:Social Environment