Abstract: Aims: Test whether a faster transition in early substance use – specifically the speed of transition from first to second use of cannabis – is associated with increased likelihood of later cannabis dependence and other problem-use outcomes.
Method: From an epidemiological study of 3824 Australian twins (mean age at time of survey = 31.2 SD = 3.0, range 21-46), 2248 participants who had reported using cannabis more than once were asked about the speed of transition from first to second use, and about their later use of cannabis and symptoms of cannabis abuse/ dependence. Regression analyses adjusted the association between speed of transition and the outcomes of cannabis daily use, abuse and/or dependence, and treatment-seeking after controlling for socio-demographic, childhood, mental health, peer and licit drug factors.
Results: After adjustment for confounders second cannabis use occurring within a week of first use was positively associated with reporting daily cannabis use (OR 2.70, 95% CI 1.75 – 4.16), abuse and/or dependence (OR 3.37, 95% CI 2.45 – 4.65) and treatment-seeking for cannabis problems (OR 2.00, 95% CI 1.10 – 3.65). Second cannabis use occurring within 3 months of first use was positively associated with abuse and/or dependence (OR 1.69, 95% CI 1.27 – 2.25). Significant differences were observed between the different transition speed groups for almost all of the socio-demographic, childhood, mental health, peer and licit drug factors tested in this analysis.
Conclusions: Rapid transition from first to second use of cannabis is associated with increased risks for frequent cannabis use and for cannabis abuse/dependence. These findings suggest that early substance-use patterns can help identify those more likely to develop problems later on, which has potential utility for targeting prevention interventions.
Professor Michael T. Lynskey, Dr Katherine I. Morley, Professor John Strang Addictions Department, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, England Associate Professor Arpana Agrawal, Professor Elliot C. Nelson Department of Psychiatry, Washington University School of Medicine, St Louis, MO, USA Dr Dixie Statham School of Social Sciences, University of the Sunshine Coast, Queensland, Australia Professor Nicholas G. Martin Queensland Institute of Medical Research, Medical Research Institute, Brisbane, Australia