Letter: Cannabis not so soft

Sir: Andreas Whittam Smith (14 October) quotes from the journal Science in his defence of the recreational use of cannabis.

On 27 June two relevant papers were published: one showed that the emotional stress in marijuana withdrawal was caused by corticotrophin releasing factor, the agent responsible for the symptoms of opiate, alcohol and cocaine withdrawal, the second that tetrahydrocannabinol (the active ingredient in marijuana) results in the same key biochemical event that seems to reinforce dependence on other drugs, from nicotine to heroin, namely the release of dopamine in part of the brain's "reward" pathway.

The journal concluded that "contrary to the popular view that marijuana is a relatively benign drug, new evidence suggests its effects in the brain resemble those of 'hard' drugs such as heroin".

Dr MARTIN HEATH

Public Affairs Officer, Brighton Division, British Medical Association

Lewes,

East Sussex