In two studies totaling 109 frequent cannabis users, psychomotor impairment peaked immediately after smoking cannabis but recovered significantly within one hour, measured by the DRUID mobile app.
Cannabis users who drive, traffic safety researchers, law enforcement, and app developers working on impairment detection.
Peak impairment immediately after use; significant recovery at 1 hour
What the researchers found
Peak psychomotor impairment occurred immediately after cannabis use, with significant recovery by one hour post-use. This pattern was consistent across both the primary Colorado study (n=70) and the Washington replication (n=39). Significant quadratic effects of time emerged in both studies.
Why it matters
There is no validated roadside test for cannabis impairment. This study suggests that psychomotor recovery happens within about an hour even for high-potency cannabis, and that app-based measures could potentially serve as impairment assessment tools.
The numbers in context
70 participants (Colorado), 39 participants (Washington replication). Peak impairment immediately after acute use. Significant recovery at 1 hour. Both studies showed significant quadratic time effects. Clinical trial NCT03522103.
How the study worked
Primary study: 70 frequent cannabis users in Colorado used the DRUID app at baseline (sober), pre-use, immediately post-use, and 1 hour post-use of self-selected high-potency cannabis. Replication: 39 participants in Washington measured every 30 minutes for 2.5 hours.
What this study cannot tell us
Naturalistic use with self-selected products limits dose control. Frequent users may have different impairment profiles than occasional users. DRUID app not yet validated as a driving impairment measure. One-hour recovery of test performance may not reflect all driving-relevant skills.
How to read the evidence
Two-study design with replication strengthens findings, but naturalistic use and lack of driving outcome validation are limitations.
When this study was published
Published in 2022.
The bigger picture
Unlike alcohol, there is no breathalyzer for cannabis. The finding that impairment is measurable by a mobile app and recovers predictably could help develop practical tools for assessing cannabis-related driving risk.
Questions still open
- Is one hour enough recovery time for safe driving? Would the DRUID app perform as well in a roadside setting? Do edibles produce a different impairment time course?
Common questions
How long are you impaired after smoking cannabis?
Do frequent cannabis users still get impaired?
Read the original research
Effects of High-Potency Cannabis on Psychomotor Performance in Frequent Cannabis Users.
Cannabis and cannabinoid research, 7(1), 107-115
Citation
Karoly, Hollis C; Milburn, Michael A; Brooks-Russell, Ashley; Brown, Mary; Streufert, Jessica; Bryan, Angela D; Lovrich, Nicholas P; DeJong, William; Cinnamon Bidwell, L. (2022). Effects of High-Potency Cannabis on Psychomotor Performance in Frequent Cannabis Users.. Cannabis and cannabinoid research, 7(1), 107-115. https://doi.org/10.1089/can.2020.0048
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