Acute cannabis consumption and motor vehicle collision risk: systematic review of observational studies and meta-analysis

To determine whether the acute consumption of cannabis (cannabinoids) by drivers increases the risk of a motor vehicle collision.

Systematic review of observational studies, with meta-analysis. DATA SOURCES: We did electronic searches in 19 databases, unrestricted by year or language of publication. We also did manual searches of reference lists, conducted a search for unpublished studies, and reviewed the personal libraries of the research team. Review methods We included observational epidemiology studies of motor vehicle collisions with an appropriate control group, and selected studies that measured recent cannabis use in drivers by toxicological analysis of whole blood or self report. We excluded experimental or simulator studies. Two independent reviewers assessed risk of bias in each selected study, with consensus, using the Newcastle-Ottawa scale. Risk estimates were combined using random effects models.