Cognitive outcomes associated with long-term, regular, recreational cannabis use in adults: A meta-analysis.
M. Lovell, Jane Akhurst, C. Padgett, M. Garry, A. Matthews
Experimental and Clinical Psychopharmacology August 1, 2020 DOI: 10.1037/pha0000326 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Meta-analysis Peer reviewed |
|---|---|
| Sample size | 1,613 |
| Population | Adults who used recreational cannabis long-term (mean ≥2 years) and regularly (mean ≥4 days/week) during abstinence (mean ≥12 hr), plus control participants; mean age about 30 years |
| Duration | Long-term use mean ≥2 years; regular use mean ≥4 days/week; abstinence mean ≥12 hr |
| Topics | Cannabis |
| Key findings | Long-term, regular recreational cannabis use was associated with small-magnitude deficits in executive function, learning and memory, and global cognition, and moderate deficits in decision making, while information processing, working memory, and attention showed small, nonsignificant differences. Cannabis use duration, age of onset, and prolonged abstinence (≥25 days) did not influence outcomes, except executive function differences were nonsignificant in prolonged-abstinence analyses. |
Abstract
Despite research advances, it remains unclear if long-term, regular cannabis use harms cognition once intoxication has passed. Our meta-analysis aimed to investigate the association between cognitive functioning and long-term (mean ≥2 years), regular (mean ≥4 days/week), recreational cannabis use in adults during abstinence (mean ≥12 hr). We searched PubMed, PsycINFO, CINAHL, Scopus, and Dissertations and Theses International for English-language articles from the date each database began until May 22, 2019. We identified study inclusion by completing abstract and full text screening using predetermined criteria and Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines. We classified cognitive performance into 6 cognitive domains (attention, executive function, learning and memory, decision making, information processing, and working memory), and included a global measure. Effect sizes were calculated for each domain using univariate meta-analyses. There were 30 studies with a total 849 participants who used cannabis (M = 30.7-years-old, SD = 5.5-years-old) and 764 control participants (M = 30.3-years-old, SD = 5.9-years-old). Cannabis was associated with significant but small-magnitude deficits in executive function, learning and memory, and global cognition, while decision making had moderate deficits. There were small-magnitude and nonsignificant group differences for information processing, working memory, and attention. Cannabis use duration, age of onset, and prolonged abstinence (≥25 days) did not influence outcomes, except group differences in executive function were nonsignificant in analyses of prolonged abstinence. Our results suggest that long-term, regular cannabis use is associated with small to moderate deficits in some cognitive domains. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
Comparable studies
Other systematic reviews and meta-analyses on cannabis, most cited first.
| Study | Year | Design | Participants |
|---|---|---|---|
| Effects of cannabis use on outcomes of psychotic disorders: systematic review People with psychotic disorders, as examined in 13 longitudinal studies | 2008 | Systematic review | |
| The Impact of Cannabis Use on Cognitive Functioning in Patients With Schizophrenia: A Meta-analysis of Existing Findings and New Data in a First-Episode Sample Patients with established schizophrenia (meta-analysis: 572) and patients with... | 2010 | Meta-analysis and cross-sectional observational study | n = 700 |
| Medicinal cannabis for psychiatric disorders: a clinically-focused systematic review | 2020 | Systematic review | |
| Neuroimaging in cannabis use: a systematic review of the literature Cannabis users and controls in neuroimaging studies | 2009 | Systematic review | |
| Human Laboratory Studies on Cannabinoids and Psychosis. Healthy human subjects and individuals with schizophrenia | 2016 | Systematic review |
Citations in the library
Cited by 20
- Use of Marijuana: Effect on Brain Health: A Scientific Statement From the American Heart Association Stroke February 10, 2022
- Unraveling the Intoxicating and Therapeutic Effects of Cannabis Ingredients on Psychosis and Cognition Frontiers in Psychology May 14, 2020
- The CannTeen study: verbal episodic memory, spatial working memory, and response inhibition in adolescent and adult cannabis users and age-matched controls Psychopharmacology April 29, 2022
- Effects of naturalistic doses of cannabis edibles on cognition and association with blood THC. Psychopharmacology March 1, 2026
- Impaired mnemonic pattern separation associated with PTSD symptoms paradoxically improves with regular cannabis use npj Mental Health Research April 24, 2025
and 15 more in the library
Cites 31
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- Telling true from false: cannabis users show increased susceptibility to false memories Molecular Psychiatry March 31, 2015
and 26 more in the library