Roger Pertwee of the University of Aberdeen and Christopher Fowler, Professor of Pharmacology at Umea University in Sweden, say marijuana is a source of compounds known as cannabinoids -- one of which, THC, the main chemical responsible for the marijuana "high," has been licensed as a medicine for suppressing nausea produced by chemotherapy and for stimulating appetite in AIDS patients.

More recently, the marijuana-based medicine Sativex was licensed both for the symptomatic relief of neuropathic pain in adults with multiple sclerosis and as an adjunctive analgesic treatment for adult patients with advanced cancer.

"THC works by targeting molecules in our bodies called cannabinoid receptors," Pertwee said in a statement. "So some current research is focused on designing drugs that only target cannabinoid receptors in the part of the body relevant to the disease in question and not the receptors in the central nervous system involved in the unwanted effects of cannabis."

Another constituent of marijuana, THCV, blocks one of the cannabinoid receptors that may provide an alternative treatment route in the fight against obesity, Pertwee said.

The findings are being presented at the Federation of European Pharmacological Societies in Manchester, England.