What do we know about the extent of cannabis use and dependence? Results of a global systematic review

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Author: Bianca Calabria, Louisa Degenhardt, Paul Nelson, Chiara Bucello, Anna Roberts, Michael Lynskey, Wayne Hall, Jennifer McLaren

Resource Type: Technical Reports

NDARC Technical Report No. 307 (2010)

EXECUTIVE SUMMARY

Aims: Systematically review peer reviewed and grey literature on the global prevalence of cannabis use and dependence. This article aims to present the first systematic review of existing data on the prevalence of cannabis use and dependence in all UN member countries. This comprehensive review systematically identified available studies in the peer reviewed and grey literature on the prevalence of cannabis use and dependence using systematic methods that are transparently reported. The result is a summary of the most recent prevalence estimates of cannabis use and dependence for each UN member country.

Methods: Multiple search strategies: a) peer-reviewed literature searches (1990-2008) using methods recommended by the Meta-analysis of Observational Studies in Epidemiology (MOOSE) group; b) systematic searches of online databases; c) Internet searches to find any other evidence of use; d) repeated consultation and feedback from experts around the globe; e) a viral email sent to lists in the HIV and illicit drug fields. Culling and data extraction followed manualised protocols, with in-built systems of cross-checking and internal consistency. Data were extracted and graded according to predefined variables and quality scored. This paper reports the most recent and highest graded prevalence estimate for the general population and school population and reports the proportion of coverage of the world‟s population for use and dependence estimates, general population and school surveys, age and sex specific estimates, and most recent year of estimates.

Results: Evidence of cannabis use or dependence was found for 99.8% of the world's population aged 15-64 years across 202 countries/territories; in 108 countries no prevalence estimates were available. School surveys were more common (90 countries) than general population surveys (58 countries). Reported point prevalence estimates of cannabis use in the general population ranged from 0% to 14.1%. Only seven countries had estimates of cannabis dependence (comprising 24.9% of the world‟s population aged 15-64 years); three countries had national estimates and four countries had sub-national estimates. General population prevalence estimates of cannabis dependence ranged from 0.1% to 1.3%.

Conclusions: There are large gaps in data on the global prevalence data of cannabis use and dependence. The improvement of global data in all countries of the world is necessary to inform policy makers to better respond to the harms related to cannabis use and dependence.