Effects of Cannabis on Psychomotor Skills and Driving Performance - a Metaanalysis of Experimental Studies

Taking part in road traffic under the influence of drugs, especially marijuana, has become a serious problem in most western societies. Thus traffic medicine is demanded to provide scientific knowledge of the effects of cannabinoids on driving performance. The present study is intended to analyse all available data on the influence of cannabinoids on psychomotor skills relevant to driving behaviour using a metaanalytic approach. About 150 experimental studies including laboratory, driving simulator and on road experiments make up the basis of our investigation. With the help of a systematic questionnaire the most important information extracted were: number, age, sex and user behaviour of the subjects, manner of drug treatment, time between drug intake and testing, tasks presented and the experimental findings concerning the drug effects. Subsequently the data were examined by the means of interferential statistics. For the first time a methodological approach is applied enabling to establish detailed statements on kind, intensity and duration of drug impairment dependent on dose, user behaviour, treatment and further variables.