Posted: 28 March 2012

Driving while under the influence of cannabis

This is a short letter written by Adam and published in the BMJ in response to an editorial piece written by Professor Wayne Hall. Professor Halls editorial is available here- Driving while under the influence of cannabis and addresses the topic of whether roadside drug testing reduces cannabis impaired driving. Below is Adams response using findings from the 2012 Global Drug Survey.

Driving while under the influence of cannabis

Dear Editor
I read with interest the editorial by Wayne Hall and the systematic review by Abridge et al in the BMJ, highlighting the increased risk of fatal road collision while driving under the influence of cannabis. As part of a wider survey on drug use patterns and harms conducted at the end of 2011 by Global Drug Survey ( in partnership with Mixmag and the Guardian newspaper, we asked current cannabis smokers about the risk of being identified as intoxicated with cannabis (without alcohol) whilst driving, if they got pulled over by the police within 2 hours of smoking a joint.
Data from over 10,000 last year cannabis users from around the world was obtained. The results from the UK, USA and Australia are outlined in table 1. The findings tend to support the cautious view put forward by Wayne Hall regarding the likely impact that roadside drug testing would have upon drug driving. For any drug driving policy to be an effective deterrent, drugged drivers must consider the risk of being stopped and subsequently detected as being under the influence as a real possibility.
Our results suggest that only a minority of current cannabis users think they would be detected as driving stoned using the present detection approaches utilised in their countries. The full results of the 2012 Global drug Survey are published exclusively in the Guardian and Mixmag on March 15 2012.

Table 1- BMJ- UK, US and Australia sample

Adam R Wintock, Consultant Addiction Psychiatrist