Suspicion of driving under the influence of alcohol or drugs: Cross sectional analysis of drug prevalence in the context of the Swiss legislation

Abstract

Driving under the influence of alcohol and drugs (DUID) is a major field of study to improve road safety. In Switzerland, during controls whether or not they follow an accident, the police can request toxicological analysis targeted either on alcohol only (ALC cases), or on drugs and alcohol (DUID cases). To evaluate both the drugs consumption on the road and whether or not these requests are well correlated with toxicological results, we built a database recording 4003 offenders (3443 males, 550 females) over a two-year period (2018-2019) in Western Switzerland. ALC case samples were then analyzed to target other substances than ethanol. We found one or more psychoactive drugs in 89% of DUID cases and alcohol alone was found in 56% of ALC cases. In ALC cases, alcohol alone was found in 72% of non-accident cases and in 52% of accident cases. This highlights an influence of accident context, inducing a too high suspicion of alcohol after accidents, and therefore an underestimation of the prevalence of other drugs. The most frequently detected drugs in DUID cases were cannabinoids (58%), ethanol (30%), cocaine (21%), benzodiazepines (11%), amphetamines (7%), opiates (6%), and antidepressants (5%). For the ALC cases, the drugs found were ethanol (84%), cannabinoids (13%), benzodiazepines (9%), antidepressants (6%), opiates (5%), cocaine (4%), methadone (3%), and amphetamines (1%). Prescription drugs, such as benzodiazepines, were common in accidents (22%) but rare in non-accidents DUID cases (5%). Thus, these drugs highly impact driving skills while being hard to suspect. This is of first concern as prescription drugs are largely found in poly-drug consumption, especially in combination with alcohol in accident cases. This emphasizes the emerging issue of prescription drugs and should motivate a strategy of prevention focused on the noxious effect of combining alcohol and prescription drugs on driving skills.