Adverse effects of cannabis and cannabinoids

Abstract

The use of cannabis for both recreational and medicinal purposes dates back for thousands of years.15 91 It is perceived widely by recreational users as a harmless drug, a view fostered by some sections of the press and even (surprisingly) by a leading medical journal.73 The opinions of 74% of doctors in a British Medical Association survey92 and of a Select Committee of the House of Lords59 that cannabis should again be available on prescription (as it was until 1971) appear to support this belief. Therapeutic uses of cannabis have recently been reviewed by the British Medical Association17 which concluded that herbal cannabis is unsuitable for medical use. Nevertheless, it was recommended that research on the value of individual pure cannabinoids in a variety of conditions, including multiple sclerosis, spinal cord injury, chronic pain and palliative care, should be encouraged. Synthetic cannabinoids such as nabilone (in the UK) and dronabinol (in the USA) already have an established use as antiemetics in nausea and vomiting associated with cancer chemotherapy. However, no drug is without unwanted effects. It is timely to review the adverse effects of cannabis, especially in view of the increased prevalence of its recreational use in the UK, increased potency of modern preparations and present interest in the therapeutic possibilities of cannabinoids. This review is based on a Medline search of articles on the pharmacology and effects of cannabis and cannabinoids 1980–1998, supplemented by comprehensive books and compendia, and standard books and articles from the older literature. Relevant books and articles were hand-searched for additional references. The search was conducted originally for reports commissioned by the Department of Health,7 the British Medical Association17 and the Ministry of Defence (unpublished), but has since been updated. The articles quoted in this review were selected from a very large bibliography as having relevance to the recreational use of cannabis and the medical use of cannabinoids in the UK today. Constraints on the number of references permitted meant further selection of original data, but most important