Psychoactive substance use and the risk of motor vehicle accidents

The driving performance is easily impaired as a consequence of the use of alcohol and/or licit and illicit drugs. However, the role of drugs other than alcohol in motor vehicle accidents has not been well established. The objective of this study was to estimate the association between psychoactive drug use and motor vehicle accidents requiring hospitalisation. A prospective observational case-control study was conducted in the Tilburg region of The Netherlands from May 2000 to August 2001. Cases were car or van drivers involved in road crashes needing hospitalisation. Demographic and trauma related data was collected from hospital and ambulance records. Urine and/or blood samples were collected on admission. Controls were drivers recruited at random while driving on public roads. Sampling was conducted by researchers, in close collaboration with the Tilburg police, covering different days of the week and times of the day. Respondents were interviewed and asked for a urine sample. If no urine sample could be collected, a blood sample was requested. All blood and urine samples were tested for alcohol and a number of licit and illicit drugs. The main outcome measures were odds ratios (OR) for injury crash associated with single or multiple use of several drugs by drivers. The risk for road trauma was increased for single use of benzodiazepines (adjusted OR 5.1 (95% Cl: 1.8–14.0)) and alcohol (blood alcohol concentrations of 0.50–0.79 g/l, adjusted OR 5.5 (95% Cl: 1.3–23.2) and =0.8 g/l, adjusted OR 15.5 (95% Cl: 7.1–33.9)). High relative risks were estimated for drivers using combinations of drugs (adjusted OR 6.1 (95% Cl: 2.6–14.1)) and those using a combination of drugs and alcohol (OR 112.2 (95% Cl: 14.1–892)). Increased risks, although not statistically significantly, were assessed for drivers using amphetamines, cocaine, or opiates. No increased risk for road trauma was found for drivers exposed to cannabis. The study concludes that drug use, especially alcohol, benzodiazepines and multiple drug use and drug–alcohol combinations, among vehicle drivers increases the risk for a road trauma accident requiring hospitalisation.