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 ps > 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 ps > 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.