Psychoactive substance use Among fatally injured traffic crash victims: A cross-sectional study Across four cities in Brazil

Objective To characterize the prevalence and patterns of psychoactive substance use among fatal traffic crash victims across four Brazilian metropolitan areas and to identify the demographic and temporal factors independently associated with substance positivity.Methods Cross-sectional study of 524 fatal traffic crash victims from Recife (n = 272), Curitiba (n = 96), Vitória (n = 93), and Belém (n = 63), March 2022–June 2024. Standardized blood toxicological screening for alcohol, cocaine (benzoylecgonine), benzodiazepines, amphetamines, and cannabis was performed at a single reference laboratory. Multivariable logistic regression identified independent predictors of alcohol and any substance positivity.Results Overall, 46.0% of victims tested positive for at least one substance. Alcohol was detected in 38.0%, with mean blood alcohol concentration (BAC) of 1.83 g/L (SD = 0.88); no significant difference across cities (p = 0.095). Cocaine or metabolites were detected in 9.9%, with uniform regional distribution (p = 0.392). Vitória showed markedly higher benzodiazepine positivity (9.7% vs. 1.0–4.4%; p = 0.019). Cannabis was not detected. Night time (OR = 2.45, 95%CI 1.63–3.67) and weekend crashes (OR = 2.05, 95%CI 1.38–3.04) were the strongest independent predictors of alcohol positivity. After adjustment, Vitória showed significantly higher odds of any substance positivity compared to Recife (OR = 1.73, 95%CI 1.01–2.98, p = 0.046).Conclusion Psychoactive substances were involved in nearly half of fatal traffic crashes across four Brazilian cities. Temporal factors—night time and weekend crashes—were the primary independent predictors of substance involvement. Vitória’s elevated benzodiazepine positivity persisted after adjustment, suggesting distinct regional prescribing patterns. These findings support temporally targeted enforcement strategies and region-specific pharmaceutical interventions.