Alcohol Impairs Thinking While Cannabis Mainly Shifts Mood, Study Finds
In a controlled trial of 28 young adults, cannabis primarily affected mood and subjective experience while alcohol primarily impaired cognitive and psychomotor performance, with combined effects that were additive at most.
Quick Facts
What This Study Found
Cannabis increased tension-anxiety, confusion, euphoria, and sedation ratings but had minimal impact on cognitive test scores. Alcohol impaired verbal recall, digit symbol substitution, and fine motor tasks but had minimal impact on mood. When combined, the effects were additive rather than synergistic.
Key Numbers
28 participants completed all four sessions; alcohol target was 80 mg/dL breath alcohol; cannabis was 12.5% THC smoked ad libitum; significant effects found on POMS tension-anxiety and confusion scales, ARCI euphoria and sedation scales, verbal free recall (immediate and delayed), and digit symbol substitution test
How They Did This
Within-subjects, double-blind, double-dummy, placebo-controlled RCT with 28 healthy cannabis users aged 19-29 who had recent binge drinking history. Four conditions tested: placebo/placebo, alcohol/placebo, placebo/cannabis (12.5% THC), and alcohol/cannabis. Cognitive and mood measures taken 75 minutes after alcohol (1 hour after cannabis).
Why This Research Matters
This controlled comparison helps separate what cannabis and alcohol each do to the brain in real time. The finding that cannabis mainly shifts subjective experience while alcohol mainly disrupts performance challenges assumptions that the two substances impair functioning in the same way.
The Bigger Picture
As cannabis and alcohol co-use becomes more common, understanding how they interact matters for impairment assessment and driving policy. This study suggests their combined effects on cognition and motor control are driven primarily by alcohol, not cannabis.
What This Study Doesn't Tell Us
Small sample of 28 young adults limits generalizability. Single-dose design does not reflect chronic co-use patterns. THC was smoked ad libitum, so doses varied between participants. Only tested one alcohol level and one cannabis potency.
Questions This Raises
- ?Would higher THC concentrations produce more cognitive impairment?
- ?Do chronic co-users develop different tolerance patterns for the combined effects?
- ?How do these lab findings translate to real-world driving impairment?
Trust & Context
- Key Stat:
- 28 participants, 4 conditions
- Evidence Grade:
- Well-designed RCT with placebo control and within-subjects design, but limited by small sample size
- Study Age:
- 2022 study
- Original Title:
- Separate and combined effects of alcohol and cannabis on mood, subjective experience, cognition and psychomotor performance: A randomized trial.
- Published In:
- Progress in neuro-psychopharmacology & biological psychiatry, 118, 110570 (2022)
- Authors:
- Wickens, Christine M(9), Wright, Madison(4), Mann, Robert E(11), Brands, Bruna, Di Ciano, Patricia, Stoduto, Gina, Fares, Andrew, Matheson, Justin, George, Tony P, Rehm, Jürgen, Shuper, Paul A, Sproule, Beth, Samohkvalov, Andriy, Huestis, Marilyn A, Le Foll, Bernard
- Database ID:
- RTHC-04299
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked Questions
Does combining cannabis and alcohol make impairment worse than expected?
Not according to this study. The combined effects were additive at most, meaning they added up but did not multiply or create unexpected new impairments.
Which substance caused more cognitive impairment in this study?
Alcohol caused significantly more cognitive and psychomotor impairment than cannabis. Cannabis mainly affected mood and subjective feelings rather than test performance.
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Cite This Study
https://rethinkthc.com/research/RTHC-04299APA
Wickens, Christine M; Wright, Madison; Mann, Robert E; Brands, Bruna; Di Ciano, Patricia; Stoduto, Gina; Fares, Andrew; Matheson, Justin; George, Tony P; Rehm, Jürgen; Shuper, Paul A; Sproule, Beth; Samohkvalov, Andriy; Huestis, Marilyn A; Le Foll, Bernard. (2022). Separate and combined effects of alcohol and cannabis on mood, subjective experience, cognition and psychomotor performance: A randomized trial.. Progress in neuro-psychopharmacology & biological psychiatry, 118, 110570. https://doi.org/10.1016/j.pnpbp.2022.110570
MLA
Wickens, Christine M, et al. "Separate and combined effects of alcohol and cannabis on mood, subjective experience, cognition and psychomotor performance: A randomized trial.." Progress in neuro-psychopharmacology & biological psychiatry, 2022. https://doi.org/10.1016/j.pnpbp.2022.110570
RethinkTHC
RethinkTHC Research Database. "Separate and combined effects of alcohol and cannabis on moo..." RTHC-04299. Retrieved from https://rethinkthc.com/research/wickens-2022-separate-and-combined-effects
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.