Although drug use has been found to be acquired in a series of stages or steps, the exact nature of this progression has not been firmly established, nor has such a process been corroborated for life periods other than adolescence. In this study, drug use data obtained from 654 adolescents were used to examine changes and sequencing of drug involvement over an eight-year period from early adolescence to young adulthood. Cannabis use peaked during late adolescence; liquor, stimulants, and nonprescription medication increased steadily over the eight-year period; hypnotics and psychedelic use increased through late adolescence and remained stable through young adulthood; and early experimental use of cigarettes decreased to more committed use over the eight-year span. In a latent variable model that did not include nonprescription drugs and cigarettes, alcohol use significantly influenced later cannabis and hard drug use, whereas cannabis use predicted later hard drug use for the earlier life period. Only the cannabis effect remained at the older age period, when drug use patterns appeared to become more stable and firmly established. However, when cigarettes and nonprescription drugs were added to the model, quite different results emerged. Based on this more comprehensive analysis, it was concluded that: There are several interrelated mini-sequences of drug involvement; cigarettes play a prominent role as a gateway to cannabis and hard drugs; and at higher levels of involvement there is a synergistic or reciprocal effect of increasing involvement. Again, the later developmental period was much more stable with somewhat different patterns of influence.
