The scientific evidence about the medical benefits of cannabis is suggestive but not conclusive, in large part because governments have placed legal obstacles in the way of proper research, but also because the smoke of marijuana contains so many compounds that need to be tested individually. But it seems that cannabis can relieve nausea (one of the most unpleasant of all symptoms when it is persistent) and some kinds of pain. Its side effects in this context are unlikely to be serious or severe. To worry about the addictive potential of a drug, for example, when the patient is unlikely to survive very long is clearly absurd, though one doctor did raise the question. I remember all too clearly the days when patients who were dying were denied pain relief by heroin because it was supposedly so addictive.

As soon as the subject of cannabis comes up, passions are aroused that seem to make it impossible for people, even doctors, to stick to the point. One correspondent pointed out that a half of American schoolchildren had tried cannabis, but this was irrelevant even to the irrelevant point he was trying to make. No one, after all, suggests that there should be no speed limits because almost every driver breaks the law within thirty seconds of starting out. There may be arguments for the decriminalization of cannabis but this is not one of them.