Patterns of drug use from adolescence to young adulthood: I. Periods of risk for initiation, continued use, and discontinuation.

Patterns of initiation, continued use, and decline in drug use are described on the basis of detailed drug histories in a longitudinal cohort representative of former New York State adolescents. In this cohort, the period of major risk for initiation to cigarettes, alcohol, and marijuana, is completed for the most part by age 20, and to illicit drugs other than cocaine by age 21. Those who have not experimented with any of these substances by that age are unlikely to do so thereafter. Initiation into prescribed psychoactive drugs occurs at a later age than for the licit and illicit drugs and continues through the age period covered by the survey. A potential maturational trend in marijuana use in this cohort is apparent with a decline beginning approximately at age 22.5 for most usage patterns. The periods of highest marijuana and alcohol usage decline beginning at ages 20-21 and contrast sharply with cigarettes which exhibit climbing rates of highest use through the end of the surveillance period (age 25). Overall patterns are similar for men and women, with men initiating all drugs at higher rates than women, except for prescribed psychoactives .