Short-term residual effects of smoked cannabis on simulated driving performance

Rationale Between periods of use, chronic cannabis consumers may display residual effects on selective cognitive functions, particularly memory and attention. Whether there are comparable deficits in real-world behaviors, such as driving, has not been thoroughly examined. Objectives The current study explored the association between driving simulator performance, cannabis use history, and demographic factors after ≥ 48 h of abstinence. Study I examined simulator performance across a broad range of use within 191 healthy cannabis users. Study II compared performance between participants with the highest cannabis use intensity and a non-cannabis-using comparison group. Methods In Study I, 191 healthy cannabis users completed a 25-minute simulated drive, following ≥ 48 h of abstinence. In Study II, a pilot study comprising a subset of 18 frequent cannabis users was compared to 12 non-using controls who completed identical driving measures in a separate study. In both studies, the main outcome was the Composite Drive Score (CDS), a global measure of driving performance comprising key driving-related variables, including standard deviation of lateral position. Results In Study I, there was no relationship between CDS, its subtests, measures of cannabis use history, or demographic variables (all p s > 0.10). In Study II, frequent cannabis users and the non-using comparison group did not differ on CDS or performance on its subtests (all p s > 0.40). Conclusions The current study did not find evidence of a residual effect of cannabis on simulated driving performance during a short period of cannabis abstinence. Future studies would benefit from inclusion of larger non-cannabis-using comparison groups.