Cannabis dependence in young adults: an Australian population study

Objectives The symptomatology of cannabis dependence remains ill-defined and its importance controversial. Compared with alcohol dependence, the symptom profile of cannabis dependence has received little attention. We aimed to (a) report cannabis use in a representative population of young adults, (b) examine cannabis dependence symptoms according to frequency in the dependence syndrome and (c) contrast the symptomatology of cannabis and alcohol syndromes. Methods 1601 young adults (mean age 20.7 years) from an Australian longitudinal cohort study (N=2032) were surveyed in 1998. Regular substance users were assessed for DSM-IV cannabis and alcohol dependence. Prevalence estimates allowed for sampling variation and attrition. Results Fifty-nine per cent reported life-time use of cannabis, 17% used at least weekly and 7% (11% males, 4% females) met criteria for cannabis dependence, Symptom prevalence in dependent cannabis users was: persistent desire 91%; unintentional use 84%; withdrawal 74%; excessive time obtaining/using 74%; continued use despite health problems 63%; tolerance 21%; and social consequences 18%. The combination of withdrawal, persistent desire and unintentional use was reported by 57%. Dependent cannabis users reported compulsive and out-of-control use more frequently than dependent alcohol users, withdrawal similarly and tolerance considerably less often. Conclusions Cannabis use appears to be normative behaviour in young Australians. Progression beyond weekly use of cannabis carries a significant risk of dependence that should be considered in the public health response. The differing profiles of cannabis and alcohol dependence, particularly with regard to craving, draws attention to the need for further study of cannabis dependence as an important and distinct disorder in young adults.