The relationship between adolescent smoking and drinking and likelihood estimates of illicit drug use.

Using data from a recent national survey of adolescent substance use, the present work examined whether adolescents with different patterns of alcohol and cigarette use differed in their estimates of the likelihood they would use an illegal drug in the future. While nonusers of either substance were the most likely to indicate that they would never use drugs in the future, users of both substances were the most likely to indicate that they would use drugs. In addition, while users of both were most likely to indicate that they were likely to use illegal substances, only-smokers were more likely than only-drinkers to indicate that they were likely to use such substances in the future. Results are discussed in terms of the gateway theory of drug sequencing and cognitive precursors of experimentation with illegal substances.