Does cannabis use increase the risk of death? Systematic review of epidemiological evidence on adverse effects of cannabis use.

OBJECTIVE

To conduct a comprehensive search of the peer-reviewed literature to assess risk of cannabis-related mortality.

METHODS

Systematic peer-reviewed literature searches were conducted in Medline, EMBASE and PsycINFO to identify data on mortality associated with cannabis use. Search strings for cannabis and mortality were used. Searches were limited to human subjects and the publication timeframe of January 1990 to January 2008. Reference lists of review articles and of specific studies deemed important by colleagues were searched to identify additional studies. A list of the selected articles was emailed to experts in the field asking for comment on completeness.

RESULTS

There is insufficient evidence, particularly because of the low number of studies, to assess whether the all-cause mortality rate is elevated among cannabis users in the general population. Case-control studies suggest that some adverse health outcomes may be elevated among heavy cannabis users, namely, fatal motor vehicle accidents, and possibly respiratory and brain cancers. The evidence is as yet unclear as to whether regular cannabis use increases the risk of suicide.

CONCLUSIONS

There is a need for long-term cohort studies that follow cannabis using individuals into old age, when the likelihood of any detrimental effects of cannabis use are more likely to emerge among those who persist in using cannabis into middle age and older. Case-control studies of cannabis use and various causes of mortality are also needed.