Two large studies reported no increase in death associated with the use of cannabis. Even diseases that might be related to long term cannabis use are unlikely to have a sizeable public health impact because, unlike users of tobacco and alcohol, most people who try cannabis quit relatively early in their adult lives, writes the author.

Exposure to smoke is generally much lower in cannabis than in tobacco cigarette smokers, even taking into account the larger exposure per puff. Existing studies do not support a link between the use of cannabis and heart disease, the leading cause of death in many Western countries, he adds. Furthermore, cannabis does not contain nicotine, a chemical contained in tobacco that is addicting and contributes to the risk of heart disease.

However, two caveats must be noted regarding available data, warns the author. Firstly, the studies to date have not followed cannabis smokers into later adult life so it might be too early to detect an increase risk of chronic diseases that are potentially associated with the use of cannabis.

Secondly, the low rate of regular cannabis use and the high rate of discontinuation during young adulthood may reflect the illegality and social disapproval of the use of cannabis. This means that we cannot assume that smoking cannabis would continue to have the same small impact on mortality if its use were to be decriminalised or legalised.

While the use of cannabis is not harmless, our current knowledge does not support the assertion that it has an adverse impact on death rates, says the author. Common sense should dictate measures to minimise adverse effects. These include discouraging use by teenagers, not using when driving or operating heavy machinery, not using excessively, and cautioning people with known coronary heart disease.

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Contact: Emma Dickinson
edickinson@bmj.com
44-207-383-6529
BMJ-British Medical Journal
18-Sep-2003