The effects of cannabis on memory function in users with and without a psychotic disorder: findings from a combined meta-analysis.
Tabea Schoeler, Joseph P. Kambeitz, I Behlke, R Murray, Sagnik Bhattacharyya
Psychological Medicine January 2016 DOI: 10.1017/s0033291715001646 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Meta-analysis Peer reviewed |
|---|---|
| Sample size | 10,958 |
| Population | Healthy individuals and patients with psychosis, comparing cannabis users and non-users |
| Topics | Cannabis |
| Keywords | Memory Meta-analyses Psychosis Δ-9-tetrahydrocannabinol |
| Key findings | Cannabis use was associated with impaired memory across several domains in healthy individuals but not in patients with psychosis, where cannabis users performed better on some memory measures. Lower depression scores, younger age, and longer abstinence attenuated the effects. The authors suggest cannabis-using patients may represent a less developmentally impaired subgroup. |
Abstract
Effect of cannabis use on memory function is a contentious issue, with effects being different in healthy individuals and patients with psychosis. Employing a meta-analytic approach we investigated the effects of cannabis use on memory function in patients with psychosis and healthy individuals, and the effect of diagnosis, memory dimension and moderating factors. A total of 88 studies were identified through a systematic literature search, investigating healthy (n = 7697) and psychotic (n = 3261) individuals. Standardized mean differences between the cannabis user and non-user groups on memory tasks were estimated using random-effects models and the effect-size statistic Cohen's d. Effects of potential moderating factors were tested using mixed-effects models and subgroup analyses. We found that cannabis use was associated with significantly (p ⩽ 0.05) impaired global (d = 0.27) and prospective memory (d = 0.61), verbal immediate (d = 0.40) and delayed (d = 0.36) recall as well as visual recognition (d = 0.41) in healthy individuals, but a better global memory (d = -0.11), visual immediate recall (d = -0.73) and recognition (d = -0.42) in patients. Lower depression scores and younger age appeared to attenuate the effects of cannabis on memory. Cannabis-using patients had lower levels of depression and were younger compared with non-using patients, whilst healthy cannabis-users had higher depression scores than age-matched non-users. Longer duration of abstinence from cannabis reduced the effects on memory in healthy and patient users. These results suggest that cannabis use is associated with a significant domain-specific impairment in memory in healthy individuals but not in cannabis-using patients, suggesting that they may represent a less developmentally impaired subgroup of psychotic patients.
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 26
- Traditional marijuana, high‐potency cannabis and synthetic cannabinoids: increasing risk for psychosis World Psychiatry September 22, 2016
- Poor medication adherence and risk of relapse associated with continued cannabis use in patients with first-episode psychosis: a prospective analysis The Lancet Psychiatry July 10, 2017
- 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
- Association between age of cannabis initiation and gray matter covariance networks in recent onset psychosis Neuropsychopharmacology March 3, 2021
and 21 more in the library
Cites 13
- Cannabidiol inhibits THC-elicited paranoid symptoms and hippocampal-dependent memory impairment Journal of Psychopharmacology October 5, 2012
- 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 Schizophrenia Bulletin July 25, 2010
- Modulation of Mediotemporal and Ventrostriatal Function in Humans by Δ9-Tetrahydrocannabinol Archives of General Psychiatry April 1, 2009
- The Effect of Cannabis Use and Cognitive Reserve on Age at Onset and Psychosis Outcomes in First-Episode Schizophrenia Schizophrenia Bulletin March 9, 2011
- Cannabis use and cognition in schizophrenia Frontiers in Human Neuroscience 2009
and 8 more in the library