Global impact of cannabis revealed

Friday October 16th, 2009

A new review of cannabis use around the world suggests it has been used by one in 25 adults aged 15 to 64 years.

Published in the Lancet, the report focuses on non-medical cannabis use. Its authors, led by Professor Wayne Hall of the University of Queensland, Australia, say that cannabis is the most widely used illicit drug by young people in high-income countries.

It has recently become popular on a global scale, they explain. But regular use "can have adverse outcomes". They examined those of most interest for public health - dependence, risk of vehicle crashes under intoxication, bronchitis and similar diseases, heart disease, and effects on lifestyle and mental health.

It is estimated that 166 million adults worldwide used cannabis in 2006. Use was highest in the USA, Australia and New Zealand, followed by Europe. It typically begins in teenage years and declines on entering full-time employment, getting married, and having children.

Dependence affects about nine per cent of users, compared with 32 per cent for nicotine and 15 per cent for alcohol. Withdrawal symptoms can include anxiety, insomnia, appetite disturbance, and depression.

Chronic bronchitis can develop, as cannabis smoke contains many of the same carcinogens as tobacco smoke. Heavy users are at higher risk of schizophrenia and problems with verbal learning, memory, and attention.

Use is also linked to poor educational attainment, but the experts say that the cause and effect of this relationship is unclear. It may be caused by pre-existing risk as well as regular cannabis use.

The authors call for further epidemiological and clinical research to "clarify the causative role of cannabis for these adverse effects."

Hall, W. and Degenhardt, L. Adverse health effects of non-medical cannabis use. The Lancet, Vol. 374, October 17, 2009, pp. 1383-91.

Tags: Australia | Brain & Neurology | Drug and Alcohol Abuse | General Health | World Health

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