Patterns of onset and cessation of drug use over the early part of the life course

This study uses retrospective drug use histories to examine the timing of drug use behavior among young people participating in alargemdomprobability survey of residents of the province of Ontario, Canada. Results reveal that the major risk period for initiation into alcohol, tobacco. and most illicit drugs begins around age 12 and is mostly over by age 22. For most drugs, peak periods of risk of initiation occur in the age range 15 to 19. For all categories of illicit drugs, results reveal high quit ntes in the first few years of use followed by il s h q decline. Differences by gender reveal higher ntes of onset for males for most drugs. Male drug users are significantly lesslikelythan femaleusen toquit usingadrug. Results arediscussedin terms oftheir implications for the development of primary prevention and early intervention programs for adolescents and young adults. Previous surveys of residential populations have often ignored the question of inci-dence or, more specifically, the timing of onset of drug use. Instead, attention has been focused largely on prevalence. While prevalence of drug use provides a useful snapshot of the number of drug users at one point in time, an overreliance on this measure has its shortcomings. Prevalence measures do not capture the full diversity or dynamics of drug use patterns over the life cycle (e.g., the number, sequencing, and timing of drug-related events) and as a result run the risk of over- or underestimating true levels of involvement for certain groups of individuals. For some, drug use behavior over time may be interspersed with periods of abstinence, while for others, it may be continuous with few or no interruptions