Jeremy Laurance: Scientists can be as irrational about drugs as the rest of us

Medical Life

The war of Nutt's mouth is warming up nicely. The Professor of Psychopharmacology from Bristol University – who until Friday was the Government's chief adviser on drugs – insisted on opening it, while Home Secretary Alan Johnson was determined to shut it.

The spat has now gone nuclear, with everyone from Lord Winston, the Labour peer, to Sir Liam Donaldson, chief medical officer, weighing in. Battle lines have been drawn between rational scientists on one side – independent, objective, evidence-driven– and irrational politicians on the other – craven, vote-chasing, 'Daily Mail'-driven. Is this a fair distinction? Er, no. Scientists are human, too. They struggle to be rational and objective, and they summon evidence to justify their positions, but they are still subject to the same whims, obsessions and prejudices as the rest of us.

Professor (David) Nutt likes to compare the risks of ecstasy (30 deaths a year) with those of horse-riding (100 deaths a year), an activity he is doubtless familiar with in the leafy environs of Bristol, where he and his four children live.

Alan Johnson responds that there isn't much horse-riding in his Hull constituency – but there are thousands of young people popping pills on a Saturday night at risk.

We are all swayed by our experience. Professor Nutt ranks the risks of cannabis as low, below those of alcohol and cigarettes. Professor Robin Murray, of the Institute of Psychiatry, who has spent his professional life studying people with schizophrenia, amongst whom cannabis smoking is epidemic, thinks they are high enough to warrant concern.

Their scientific disagreement calls to mind the scene in Woody Allen's 1977 film 'Annie Hall', in which each of the main characters answers a question from their therapist about how often they have sex. "Hardly ever," replies Alvy Singer, the neurotic New Yorker; "All the time," says Annie Hall, his lover. But both agree it is three times a week.

Experience shapes our view of statistics. Doctors talk about the "last case" phenomenon. If your GP has just had a patient erupt in boils on medicine A, be prepared to accept a prescription for medicine B, even though A may the standard therapy for your condition.

The dominance of experience over evidence was demonstrated in last week's row over caesareans. Latest figures showed Britain's caesarean rate, at one in four of all births, is way above the 15 per cent rate the World Health Organisation has said should not be exceeded. So how did the professional bodies react? With diametrically opposite responses. The Royal College of Midwives, whose members deliver low-risk women, said the figures showed Britain's caesarean rate was too high. The Royal College of Obstetricians, which delivers specialist care to high-risk women, said Britain's rate was in line with other European countries and the status quo was fine. Facts are sacred – but everyone views them from their own perspective.