A major focus of this project concerned the extent to which early onset cannabis use may be associated with escalation in drug use and the development of illicit drug abuse/dependence. To explore the utility of the current data for addressing these issues, we present here a series of analyses describing the age of onset of cannabis use and the links between early onset cannabis use and later risks of other illicit drug use and drug abuse/dependence. Onset of cannabis use typically occurred during the teenage years with 78% of lifetime cannabis users reporting initiating use before age 20. Again, there was evidence of very small sex differences with early onset of cannabis use being more common among males than among females: for example, 57.5% of male cannabis users reported initiating cannabis use before age 18, compared with 50.9% of females.
