Cannabis use among motorcyclists in Brazil: prevalence and associated factors from a cross-sectional study in two cities

Objective To estimate the prevalence of cannabis use among motorcyclists and identify factors associated with tetrahydrocannabinol (THC) positivity in two major Brazilian cities.Methods A cross-sectional roadside study was conducted with motorcyclists in São Paulo (2023) and Campinas (2026), Brazil. Participants completed a structured questionnaire and provided oral fluid samples, which were analyzed using liquid chromatography–tandem mass spectrometry. Multivariable logistic regression was used to assess factors associated with THC positivity.Results Among 502 motorcyclists, 13.1% tested positive for at least one psychoactive substance, with THC detected in 9.6%. In adjusted analyses, age showed a non-linear association with THC positivity, with the probability of testing positive peaking at approximately 32 years and declining thereafter (age: aOR = 1.636, 95% CI: 1.080–2.480; age2: aOR = 0.992, 95% CI: 0.986–0.998). A history of prior motorcycle crash was independently associated with higher odds of THC positivity (aOR = 2.623; 95% CI: 1.053–6.534), though this estimate should be interpreted with caution given the wide confidence interval. The association between app-based delivery work and THC positivity was not statistically significant after adjustment.Conclusions Cannabis use was frequently identified among motorcyclists, a high-risk group for road traffic injuries. These findings underscore the importance of strengthening monitoring strategies and generating evidence to support policies addressing drug-impaired driving in Brazil.