Occasional cannabis users showed slowed reaction time and impaired memory after smoking, but daily users showed tolerance to these effects while still taking longer on a driving-related decision task.
People interested in cannabis impairment, tolerance, and driving safety.
Daily users showed tolerance to reaction time and memory effects
What the researchers found
Occasional users showed significant decrements in reaction time and short-term memory after smoking cannabis. Daily users did not show these impairments (consistent with tolerance) but did take more time on a gap acceptance driving task, though their accuracy remained unchanged.
Why it matters
Understanding how tolerance affects cannabis impairment is critical for assessing driving safety and workplace policies. This study suggests daily users develop tolerance to some cognitive effects but may still show subtle changes in real-world decision tasks.
The numbers in context
Occasional users: n=23. Daily users: n=31. Non-users: n=32. Ages 25-45. THC concentration: 15-30%. Testing occurred approximately 60 minutes after smoking. Daily users took more time on gap acceptance but maintained accuracy.
How the study worked
Participants aged 25-45 completed an iPad-based test battery before and 60 minutes after smoking cannabis. Three groups compared: occasional users (n=23), daily users (n=31), and non-users (n=32). Cannabis was self-supplied flower with 15-30% THC, self-administered ad libitum.
What this study cannot tell us
Small sample sizes per group. Self-administered, self-supplied cannabis means doses varied. Only one time point (60 minutes) measured. iPad-based tests may not fully capture real-world driving complexity. No blood THC levels reported.
How to read the evidence
Controlled experimental design with appropriate comparison groups, though limited by small sample sizes, self-dosed cannabis, and single-timepoint assessment.
When this study was published
Published in 2024 in Journal of Cannabis Research.
The bigger picture
Cannabis impairment testing is a major policy challenge because tolerance makes effects highly variable across users. This study supports the idea that frequent users are less acutely impaired on some measures but still show changes on tasks that mimic real-world driving decisions.
Questions still open
- Does the daily users finding on gap acceptance (slower but equally accurate) represent impairment or a deliberate compensation strategy? Would tolerance findings hold at higher THC doses? How long do these acute effects last in occasional versus daily users?
Common questions
Do daily cannabis users develop tolerance to impairment?
Were daily users more accurate on the driving task despite being slower?
Read the original research
Effects of acute cannabis inhalation on reaction time, decision-making, and memory using a tablet-based application.
Journal of cannabis research, 6(1), 3
Citation
Brooks-Russell, Ashley; Wrobel, Julia; Brown, Tim; Bidwell, L Cinnamon; Wang, George Sam; Steinhart, Benjamin; Dooley, Gregory; Kosnett, Michael J. (2024). Effects of acute cannabis inhalation on reaction time, decision-making, and memory using a tablet-based application.. Journal of cannabis research, 6(1), 3. https://doi.org/10.1186/s42238-024-00215-1
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