Predicting Adolescent Cannabis Use Persistence into Adulthood

Two issues central to the debate about legalization of cannabis are the potential for cannabis addiction and the "gateway" theory to "harder" drug use. It is argued that legal availability of cannabis will lead to an increase in adolescent experimentation with the substance and eventually to dependency. This inquiry sought to establish some foundation upon which a reasonable discussion of experimental use and its relationship to use continuation into adulthood and to dependency could proceed. A retrospective longitudinal analysis of cannabis use in Malta revealed adolescents who had a lifetime use rate of 6 or more times by age 16 had a 25% continuation rate to age 40. Between 40% and 49.5% of those who used 20 or more times by age 16 were likely daily or near daily users in the 18-24 age cohort. When one considers the findings that the 18-24 age cohort has a similar rate of use as the 40 year old cohort, the concept of "maturing out" of substance use does not appear to apply. If legalization of cannabis makes it readily available to adolescents and if adolescent experimentation increases, then it is reasonable to conclude that the numbers of adults using cannabis to at least age 40 and the number dependent upon it will increase significantly.