They've proved that cannabis makes you aggressive. Yeah, right, says Marc Abrahams

Lock three men in a room, make them smoke cannabis, and then try to provoke them into being hostile. Thirty years ago a team of American doctors actually conducted this daring experiment. They then described it in a report called Marijuana and Hostility in a Small-Group Setting.

The conventional wisdom at the time said that cannabis would make people less hostile, that it would tend to quieten aggressive behaviour even in people who tended to be pugnacious. Such was the widespread belief among cannabis smokers, and also among people who knew cannabis smokers, which included a large proportion of the American population.

But conventional wisdom is not always right. Several aggressive political figures voiced with certainty that cannabis had pernicious, vicious effects, and that directly or indirectly its use led to hostility, violence and worse. Several medical eminences agreed. This experiment was an attempt to settle the question.

Carl Salzman and Richard Shader were co-directors of the Psychopharmacology Research Laboratory at Harvard Medical School in Boston. Together with a colleague, Bessel A van der Kolk, they recruited 60 brave volunteers, all healthy men between the ages of 21 and 30, all with prior experience of smoking cannabis.

The men were divided into groups of three. Half the groups would be smoking real cannabis. The others would smoke placebos.

The doctors asked each group to perform a series of actions. First, the group met for 10 minutes, looking at a card with a picture on it and trying to concoct a consensus description of the picture. Then each individual thoroughly smoked one cigarette. The cigarette in some groups did, and in other groups did not, contain THC, the most famous psychoactive constituent chemical in cannabis.

Each group was then told, with cold hauteur, that its picture description was "inadequate". This, the doctors explain in their report, "was conceived of as an experimental frustration stimulus". The group then tried to reach consensus on a new, better description of the picture.

The results were largely as expected. Upon being frustrated, the general hostility levels of the non-cannabis smokers went up, and those of the cannabis smokers went down.

But there was one, quite specific, surprise. The doctors' report puts it plainly: "Marijuana produced a small but statistically significant increase in sarcastic communications."

Cannabis-enhanced sarcasm may seem a wispy thing to notice or worry about. But to public policymakers charged with leading the large, sometimes fractious American populace, it seems to have seemed a danger. This apprehension may not exist in the UK, where public politicians hone and pride themselves on an ability to ignore sarcasm.

(Thanks to Kelly McLaughlin for bringing this to my attention.)
