The Association Between Cannabis Use and Schizophrenia: Causative or Curative? A Systematic Review
Shweta Patel, Sahar Khan, M Saipavankumar, Pousettef Hamid
Cureus July 21, 2020 DOI: 10.7759/cureus.9309 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Systematic review Randomized Peer reviewed |
|---|---|
| Topics | Cannabis |
| Citations | 69 |
| Key findings | The authors conclude that the THC component of cannabis may be the main cause of psychosis and schizophrenia in at-risk populations and may exacerbate symptoms and worsen prognosis in diagnosed patients. They report that six studies supported a therapeutic effect of CBD, but describe this evidence as minimal, with low safety and efficacy data warranting more research. |
Abstract
Marijuana is one of the most abused substances in the world. Marijuana is getting legalized around the world. So, it is crucial to understand its effect on our mental health. Its impact on the schizophrenia spectrum needs our special attention. Even though marijuana has been around for a long time, its exact effects are still unknown. Schizophrenia is a chronic illness affecting approximately 20 million people worldwide. Schizophrenia and cannabis seem to have a close relationship, and we want to explore this. We want to know if marijuana is causing, exacerbating, or treating schizophrenia. This systematic review explores this question. We searched online resources like PubMed, PubMed Central, Cochrane Library, and Google Scholar for systematic reviews, traditional reviews, randomized controlled trials, and meta-analysis on cannabis and schizophrenia/ psychosis. We included human studies published in peer-reviewed journals in the English language in the last five years. After reviewing 96 initial results of our search, we excluded 25 duplicates, 29 abstracts, and 18 irrelevant articles. We did a quality assessment for the remaining 24 studies using various quality assessment tools. After the quality assessment, we found 12 articles were of low quality and excluded those. We included the remaining 12 final studies in our systematic review. Out of these 12 studies, five were traditional reviews, two systematic reviews, two meta-analysis, and three observational studies. Six of the articles were on cannabis's effect on just schizophrenia or psychotic disorder. The other six included schizophrenia plus other psychiatric or neurological illnesses. Ten of the studies had data supporting the causative link between cannabis and schizophrenia. Eight records had data supporting the exacerbating effect of marijuana. Six studies had data supporting the therapeutic effect of the cannabidiol (CBD) component of cannabis. From the current data, we can conclude that the tetrahydrocannabinol (THC) component of cannabis can be the main culprit causing psychosis and schizophrenia in the at-risk population. THC can also be the one exacerbating symptoms and causing an adverse prognosis in already diagnosed patients. Even though CBD shows therapeutic effects and THC opposing effects, the data is minimal and low safety and efficacy warrants more research. The relation between cannabis and schizophrenia needs further investigation. We need more case-control studies and clinical trials with a larger population to get conclusive data.
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 17
- A Proteomic View of Cellular and Molecular Effects of Cannabis Biomolecules September 27, 2021
- The Construct of Medical and Non-Medical Marijuana—Critical Review International Journal of Environmental Research and Public Health February 27, 2022
- The Effects of Cannabidiol and δ-9-Tetrahydrocannabinol in Social Cognition: A Naturalistic Controlled Study Cannabis and Cannabinoid Research July 26, 2022
- The Relationship Between Cannabis Use and Schizophrenia As a Risk Factor or For Its Therapeutic Potential: A Systematic Review of Evidence Cureus September 20, 2025
- Intensity of Psychoactive Substance Use Affects the Occurrence of Prodromal Symptoms of Psychosis. Journal of Clinical Medicine January 28, 2024
and 12 more in the library
Cites 3
- Medicinal cannabis for psychiatric disorders: a clinically-focused systematic review BMC Psychiatry January 16, 2020
- Cannabis and Psychosis Through the Lens of DSM-5 International Journal of Environmental Research and Public Health October 28, 2019
- Associations between Adolescent Cannabis Use and Brain Structure in Psychosis Psychiatry Research Neuroimaging March 28, 2018