Prevalence of psychotropic drug use prior to driving

- Driving under the influence of drugs is poorly characterised in most countries.
- Painkillers, antidepressants, anti-nausea and anxiolytics were taken prior to driving.
- Cannabis was the most common illegal drug taken before driving.
- Combinations of drugs were frequently take prior to driving.
- Drivers need to be better informed of the impairments caused drug combinations.

The prevalence and adverse consequences of alcohol-impairment in drivers of motor vehicles is well documented. By comparison, driving under the influence of legal and illegal psychotropic drugs is poorly characterised in most countries. This study was conducted to investigate the prevalence of drugged driving in New Zealand, and to obtain a profile of the types of drugs most commonly taken prior to driving. A stratified sample (n=2000) of drivers (representative of the age distribution of licensed drivers) from across NZ completed a telephone survey (41% male, mean age 47.26 years). Additional participants completed the survey online (n=434; 28% male, mean age 34.54 years) Participants were asked to report their use of 17 different types of prescription and non-prescription psychoactive drugs in the previous 12 months and to indicate if they had taken them less than 3 h prior to driving. The legal drugs most commonly taken prior to driving (other than alcohol, consumed by 13% of the sample) were strong painkillers (11%), antidepressants (7%) anti-nausea medication (4%) and anti-anxiety medication (3%). Other than cannabis, taken by 4% of the sample, the prevalence of illegal drug use less than 3 h before driving was generally low (<0.1%). Male gender and younger age and higher income were associated with driving under the influence of alcohol and less than 3 h after illegal drug use. A small but significant proportion (12%) of drivers reported taking combinations of drugs prior to driving. Combinations of legal drugs (typically painkillers) were most common (6%), however alcohol was taken with other drugs by 38% of the combined drug users. This is of particular concern as drugs combined with alcohol lead to significantly higher crash risks and driving related impairments than drugs or alcohol alone. Efforts should be made to better communicate this risk to drivers.