The Health and Safety Executive (HSE) today published research which examined the effects of cannabis on mental (cognitive) performance.
It concludes that there was some evidence of mild cognitive impairment, but further research would be needed to reach a better understanding of the effects of cannabis use on workers’ ability to carry out operations affecting health and safety.
The work was commissioned by HSE because cannabis is the most commonly used recreational drug in Britain, and it wished to find out more about how cannabis use could affect health and safety at work.  It was carried out by GW Pharmaceuticals Limited, the company licensed by the Home Office to carry out a pharmaceutical research and development programme to develop  non-smoked cannabis-based prescription medicines.  The study offered HSE a unique opportunity to measure the effects of cannabis preparations produced from plants grown in a controlled environment.  This was important because ‘street’ cannabis varies in its strength and composition.
Six healthy volunteers received doses of cannabis-based medicine, in quantities higher than would be used in medical treatments, to induce intoxication similar to that experienced by recreational users of smoked cannabis seeking a ‘high’.  Assessments were made on a number of functions including memory, reaction time and attention.
The results show some evidence for mild impairments in a few of the measurements which persisted for a few hours after the cannabis was given.  Such results may have safety implications.  However, because of the very small number of people tested and the fact that it was a laboratory-based study rather than a study in the ‘real’ world, the results are to be treated with caution.