Gender differences in driving under the influence of psychoactive drugs: Evidence mapping of real case studies and meta-analysis

Background: Very few studies have examined predictors of Driving Under the Influence (DUI) as a function of gender. This oversight is relevant, because analyzing gender differences prevents generalization of results observed in men, who still currently account for the majority of drivers worldwide, to women. The aim of this study is to analyze the prevalence of DUI of drugs in men and women reported in real case studies published in the last two decades, and to assess gender differences in risky DUI behaviour. Methods: PubMed, Scopus, Web of Science were searched for eligible studies in May 2021; a follow-up literature search was conducted in August 2021. Real-case studies of drivers convicted for DUI of psychoactive drugs with positive toxicological confirmatory analysis were included. The extracted outcome was the prevalence of positive findings of men and women for cocaine, cannabinoids, amphetamine-like drugs, opioids, and psychoactive prescription drugs. A meta-analysis of random effects estimates was performed to investigate the change in the size of the overall effect (by Cohen d standardized mean difference test). A Mann Whitney U test was performed to test for differences between genders. Results: Of the 2877 studies screened, 439 were retrieved in full-text and 26 were included. The meta-analysis showed a significant higher prevalence among men for cocaine (1.8% vs 0.9%; p < 0.001), cannabinoids (3.5% vs 1.6%; p = <0.01) and amphetamine-like drugs (1.2% vs 0.6%; p < 0.01). Surprisingly, no differences were observed in the use of opioids (2.3% vs 2.2%; p = 0.45) and benzodiazepines/Z-drugs (2.9% vs 3.7%; p = 0.52). Conclusion: Contrary to the extraordinary number of real-case studies reported in literature, only a few papers differentiate the prevalence of DUI between men and women. This can lead to an underestimation of the influence of gender in DUI phenomenon or complicate the evaluation of the results for some classes of substances, as observed for medications and opioids. The primary goal in the future will be to collect the data concerning DUI drivers following shared and homogeneous methodologies, in order to allow the analysis of data disaggregated by gender, which can be used for monitoring evolving trends and developing gender-specific targeted prevention and enforcement efforts.