Toxicological findings in suspected drug-impaired drivers in Norway - Trends during 1990-2015

- Trends in drug use among suspected drug-impaired drivers during 26 years.
- All toxicological analyses have been performed in the same laboratory.
- A large increase in both suspected drug-impaired drivers and drug-positive samples.
- During 2000-15: particularly marked increase in THC findings among drivers aged <30.
- During 2000-15: particularly marked increase in amphetamines among drivers aged >40.

This study describes trends in drug use among drivers suspected of driving under the influence of drugs, apprehended by the police in Norway during 1990-2015. Chromatographically determined toxicological findings in blood samples were retrospectively investigated. Drug findings above defined cut-off concentrations were considered positive; hence making the annual prevalence comparable during the 26 years studied.Blood samples from 112,348 drivers were included, of which 63% were positive for drugs; 43% had combined drug with alcohol or other drugs. In total, 87% of the drug-positive drivers were men, and a higher proportion of them were positive for illicit drugs compared to the women. Benzodiazepines and related drugs were found in 57% of the drug-positive drivers, stimulants in 51%, cannabis (tetrahydrocannabinol, THC) in 34%, and opioids in 18%. The types of benzodiazepines and opioids changed over time. The age distribution also changed; the proportion of drug-positive drivers above 40 years of age increased for all drug classes. The annual number of suspected drug-impaired drivers increased by 122% from 1990 to 1999, and by 54% from 2000 to 2015; the annual number of drug-positive samples increased by 260% from 1990 to 1999, and by 60% from 2000 to 2015. During 2000-2015, an increasing prevalence of amphetamines was found among suspected drug-impaired drivers above age 30; the highest rate of increase was observed among those at or above age 40. In the same period, the prevalence of benzodiazepines and related drugs decreased among all age groups, whereas the prevalence of THC increased; the highest prevalence and rate of increase were among suspected drug-impaired drivers under the age of 30. The results from this study indicate a slight change in the types of drugs used by drivers in Norway.