The trouble with evidence

Professor Nutt is in the news again. David Nutt is one of the UK’s leading neuroscientists, and chairs the Advisory Committee on the Misuse of Drugs, which advises the UK Government on drugs classification. He first hit the headlines earlier this year, when he pointed out that the drug ecstasy was no more harmful than horse riding and got a dressing down from the then home secretary. Fiona Fox wrote a great piece about this on her blog.

Now, he has criticised a government decision on the classification of cannabis, pointing out that it compares favourably to legal drugs, alcohol and tobacco, on many measures of harm. These debates around drug classification highlight two key issues that we need to face up to if we are serious about evidence based policy making:

  • Policy debates seldom start from a blank sheet of paper. So the consequences of taking an evidence-based approach can be wide-ranging. In the case of drugs policy, the big problem is the existence of two addictive and harmful drugs that are widely accepted in society – alcohol and tobacco. Whatever the evidence says about relative harm, the choices of either banning these substances or adding to the list of legal drugs are both politically fraught.
  • Evidence often goes against the prejudice that people have, or the so-called common sense view. The real value of taking an evidence based approach is to challenge the accepted view. Evidence to confirm the accepted view is nice, but it is the challenge that should really make a difference. The irony is that when evidence, however rigorous, goes against the commonly held view it is most likely to be ignored.

I firmly believe we need to face up to these issues as evidence-based approaches will lead us to better outcomes. And I also hope that Professor Nutt will be treated a little better this time. We need to hear the evidence however politically unpalatable it might be.

Update [30 October]:

So it turns out that Professor Nutt has been sacked as chair of ACMD. How ironic, in the week a new Government report opened with the words:


If government decisions are to be robust, they need to be based on all relevant evidence. Science and engineering are key elements of this evidence base.