| Authors: Mastropietro KF, Rattigan JA, Paltin D, Umlauf A, Grelotti DJ, Fitzgerald RL, Grant I, Marcotte TD |
| Abstract:Objective:
During periods of abstinence, some very frequent cannabis consumers may display residual cognitive effects, which usually resolve within days to a month. Largely unexamined is whether residual effects are seen in real-world behaviors, such as driving. Using driving simulators, one study (Dahlgren et al., 2020) found that, compared to non-users, users with an earlier age of use onset exhibited decrements in performance during a short period of non-use (> 12 hours), whereas another study found users evidenced less swerving (better performance) than non-users following > 8 hours of abstinence (Brooks-Russell et al., 2021). The current study examined whether non-acute, short-term residual effects of cannabis are seen with driving simulator performance within cannabis users with a range of use patterns, and non-using controls, and whether any deficits are associated with use history or demographic factors.
Participants and Methods:
191 healthy cannabis users (using > 4 times in the last 30 days) abstaining from cannabis use for > 48 hours (in part confirmed by saliva analysis) and 13 healthy non-users completed a 25-minute drive on a high-fidelity driving simulator. The drive included both urban and rural driving segments, and specific challenges (e.g., crash avoidance). The main outcome was the Composite Drive Score (CDS), a global measure of driving performance comprised of key variables, including standard deviation of lateral position (SDLP, i.e., swerving), a divided attention task during the drive, and car following abilities (Marcotte et al., 2022). For multivariate analyses, users were grouped together and then divided into tertiles for high, middle, and low cannabis use based upon total grams of cannabis consumed in the past 6 months, with the highest using group averaging approximately 4 joints per day.
Results:
The average self-reported abstinence period for cannabis users was 5.35 days (SD = 5.87), with greater use over the previous six months correlating with shorter abstinence periods (r = -.17, p = .035). No differences were found on CDS between the cannabis users as a group and non-users (p = .66), nor when comparing the high, middle, and low cannabis-using tertiles to non-using controls (all ps > .66). Furthermore, no differences were found among the cannabis using group/tertiles and controls on the subtests comprising the CDS (all ps > .14). Within the cannabis using participants, performance on the driving measures was unrelated to indicators of past use or demographic variables (all ps > .10).
Conclusions:
As the largest study of its kind to date, and including a carefully screened non-using comparison group, the current study did not find evidence of a dose-effect relationship between cannabis use over 6 months and decrements in simulated driving performance during brief periods of abstinence. This suggests that the immediate short-term residual cognitive effects of cannabis might not translate directly to reductions in select overlearned real-world behaviors, such as driving, and highlights the challenges in extrapolating specific neuropsychological findings to the real world. Future studies would benefit from inclusion of larger non-cannabis-using comparison groups, which might increase sensitivity to deficits, and analyzing on-road performance. |