Cannabis Users Showed Lower Alertness and Slower Cognition at Work But No More Workplace Errors
A study of cannabis users versus controls in a work context found impairments in alertness, response speed, working memory, and episodic recall, but cannabis users did not report more workplace errors, with effects appearing as "hangover" and fatigue-related patterns.
Quick Facts
What This Study Found
Cannabis users and controls completed laboratory cognitive tests before and after work at the start and end of a working week, along with daily workplace performance diaries.
Cannabis use was associated with lower alertness and slower response organization across testing sessions. Users experienced working memory problems at the start of the working week (suggesting a "hangover" effect from weekend use) and psychomotor slowing and poorer episodic recall at the end of the working week (suggesting fatigue-related vulnerability).
Despite these laboratory-measured impairments, cannabis users reported no more workplace errors than controls in their daily diaries. The pattern suggested two types of effects: a hangover effect that may increase with frequency of use, and a subtle cognitive effect more apparent under cognitive load or fatigue.
Key Numbers
Cannabis users showed: lower alertness, slower response organization, working memory problems (start of week), psychomotor slowing and poorer episodic recall (end of week). No more self-reported workplace errors than controls.
How They Did This
Observational study comparing cannabis users and controls on laboratory cognitive tasks (mood, cognitive function) administered pre- and post-work at the start and end of a working week. Daily workplace diaries tracked self-reported performance errors.
Why This Research Matters
This is one of the few studies to examine cannabis effects in a real-world work context rather than just a laboratory. The finding that measurable cognitive impairments did not translate to more workplace errors suggests either compensation strategies or that the tests are more sensitive than job demands.
The Bigger Picture
The disconnect between laboratory cognitive decrements and real-world workplace performance highlights the challenge of translating cognitive testing results into predictions about functional impairment. It also raises questions about how much cognitive reserve people have to compensate for drug-related subtle deficits.
What This Study Doesn't Tell Us
Self-reported workplace errors may not accurately capture actual performance differences. Cannabis use patterns were not precisely controlled or verified. The sample size is not specified in the abstract. The studies occurred over a single working week, limiting conclusions about longer-term effects.
Questions This Raises
- ?Would objective workplace performance measures (rather than self-report) reveal differences?
- ?Do the cognitive impairments translate to safety-relevant errors in higher-risk occupations?
Trust & Context
- Key Stat:
- Laboratory cognitive impairments found, but no increase in self-reported workplace errors
- Evidence Grade:
- Observational study with ecological validity (real work context) but limited by self-reported outcomes and lack of objective workplace performance measures.
- Study Age:
- Published in 2006. Workplace cannabis research has expanded, particularly as legalization has raised new workplace policy questions.
- Original Title:
- Cannabis use, cognitive performance and mood in a sample of workers.
- Published In:
- Journal of psychopharmacology (Oxford, England), 20(1), 14-23 (2006)
- Authors:
- Wadsworth, E J K, Moss, S C, Simpson, S A, Smith, A P
- Database ID:
- RTHC-00252
Evidence Hierarchy
Watches what happens naturally without intervening.
What do these levels mean? →Frequently Asked Questions
Does cannabis affect work performance?
This study found measurable cognitive effects (lower alertness, slower response, memory issues) in cannabis users during work-related testing, but they did not report more workplace errors. The effects appeared as "hangover" patterns at the start of the work week and as enhanced sensitivity to fatigue by week's end.
Is there a cannabis "hangover" effect?
Yes. Users showed working memory problems at the start of the working week, suggesting residual effects from weekend cannabis use. By the end of the week, a different pattern emerged with psychomotor slowing and memory recall problems, suggesting accumulated fatigue effects.
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Cite This Study
https://rethinkthc.com/research/RTHC-00252APA
Wadsworth, E J K; Moss, S C; Simpson, S A; Smith, A P. (2006). Cannabis use, cognitive performance and mood in a sample of workers.. Journal of psychopharmacology (Oxford, England), 20(1), 14-23.
MLA
Wadsworth, E J K, et al. "Cannabis use, cognitive performance and mood in a sample of workers.." Journal of psychopharmacology (Oxford, 2006.
RethinkTHC
RethinkTHC Research Database. "Cannabis use, cognitive performance and mood in a sample of ..." RTHC-00252. Retrieved from https://rethinkthc.com/research/wadsworth-2006-cannabis-use-cognitive-performance
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.