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
Murat Yücel, Emre Bora, Dan Ian Lubman, Nadia Solowij, Warrick J. Brewer, Sue Cotton, Philippe Conus, Michael Takagi, Alexander Fornito, Stephen James Wood, Patrick D. Mcgorry, Christos Pantelis
Schizophrenia Bulletin July 25, 2010 DOI: 10.1093/schbul/sbq079 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Meta-analysis and cross-sectional observational study Peer reviewed |
|---|---|
| Sample size | 700 |
| Population | Patients with established schizophrenia (meta-analysis: 572) and patients with first-episode psychosis (85) plus 43 healthy nonusing controls |
| Topics | Cannabis |
| Citations | 256 |
| Key findings | Patients with schizophrenia or first-episode psychosis and a history of cannabis use showed better neuropsychological functioning than nonusing patients. This association may be driven by a subgroup of "neurocognitively less impaired" patients who developed psychosis only after relatively early cannabis initiation. |
Abstract
Cannabis use is highly prevalent among people with schizophrenia, and coupled with impaired cognition, is thought to heighten the risk of illness onset. However, while heavy cannabis use has been associated with cognitive deficits in long-term users, studies among patients with schizophrenia have been contradictory. This article consists of 2 studies. In Study I, a meta-analysis of 10 studies comprising 572 patients with established schizophrenia (with and without comorbid cannabis use) was conducted. Patients with a history of cannabis use were found to have superior neuropsychological functioning. This finding was largely driven by studies that included patients with a lifetime history of cannabis use rather than current or recent use. In Study II, we examined the neuropsychological performance of 85 patients with first-episode psychosis (FEP) and 43 healthy nonusing controls. Relative to controls, FEP patients with a history of cannabis use (FEP + CANN; n = 59) displayed only selective neuropsychological impairments while those without a history (FEP - CANN; n = 26) displayed generalized deficits. When directly compared, FEP + CANN patients performed better on tests of visual memory, working memory, and executive functioning. Patients with early onset cannabis use had less neuropsychological impairment than patients with later onset use. Together, these findings suggest that patients with schizophrenia or FEP with a history of cannabis use have superior neuropsychological functioning compared with nonusing patients. This association between better cognitive performance and cannabis use in schizophrenia may be driven by a subgroup of "neurocognitively less impaired" patients, who only developed psychosis after a relatively early initiation into cannabis use.
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 | |
| 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 | |
| Cannabis, a cause for anxiety? A critical appraisal of the anxiogenic and anxiolytic properties | 2020 | Systematic review |
Citations in the library
Cited by 47
- Gone to Pot – A Review of the Association between Cannabis and Psychosis Frontiers in Psychiatry May 22, 2014
- Susceptibility of the adolescent brain to cannabinoids: long-term hippocampal effects and relevance to schizophrenia Translational Psychiatry November 27, 2012
- Pathways from Cannabis to Psychosis: A Review of the Evidence Frontiers in Psychiatry 2013
- Alcohol confounds relationship between cannabis misuse and psychosis conversion in a high‐risk sample Acta Psychiatrica Scandinavica January 9, 2015
- Cannabis use and nonuse in patients with first-episode psychosis: A systematic review and meta-analysis of studies comparing neurocognitive functioning European Psychiatry 2020
and 42 more in the library
Cites 11
- Causal association between cannabis and psychosis: examination of the evidence The British Journal of Psychiatry January 30, 2004
- Cannabis use and cognition in schizophrenia Frontiers in Human Neuroscience 2009
- The effect of cannabis on the brain: can it cause brain anomalies that lead to increased risk for schizophrenia? Current Opinion in Psychiatry March 1, 2008
- The acute effects of synthetic intravenous Delta9-tetrahydrocannabinol on psychosis, mood and cognitive functioning. Psychological Medicine October 2009
- Synthetic delta-9-tetrahydrocannabinol (dronabinol) can improve the symptoms of schizophrenia. Journal of Clinical Psychopharmacology June 2009
and 6 more in the library