The preceding chapters have described developmental patterns of use in different populations, as well as risk and protective factors for progression to various stages of use. With the exception of the research of Golub and Johnson, the studies are based on representative longitudinal school or community samples of adolescents and young adults selected from different regions or cities in the United States. The representative samples do not extend through the entire period of risk for initiation of illicit drugs. The older sample described by Golub and Johnson in Chapter 5 is of particular interest because it consists of deviant individuals. It is not clear, however, to what extent the patterns observed in that sample are affected by factors that determine criminal behavior and apprehension by the police. In all the studies, the conceptualization of stages is characterized by two features. All illicit drugs other than marijuana are aggregated into a single class and no attempt is made to determine an order among these drugs. Furthermore, with the exception of the chapter by Labouvie and White (Chapter 2), the focus is mostly on progression from one class of drugs to another; no attention is paid to progressive involvement within a particular drug class.

We take advantage of a large national data set to explore previously unexplored substantive and methodological issues related to drug use progression.