THC appears to cause and worsen psychosis while CBD may have therapeutic potential, but evidence is limited
A systematic review of 12 studies found 10 supporting a causal link between cannabis and schizophrenia, 8 showing symptom worsening, and 6 supporting therapeutic effects of CBD.
Quick Facts
What This Study Found
After screening 96 articles and including 12 final studies (5 traditional reviews, 2 systematic reviews, 2 meta-analyses, 3 observational), 10 studies supported a causative link between cannabis and schizophrenia, 8 supported symptom exacerbation, and 6 supported therapeutic effects of CBD. The evidence points to THC as the primary risk component while CBD may counteract psychotic symptoms.
Key Numbers
96 initial results; 12 final studies included; 10 supported causative link; 8 supported exacerbation; 6 supported CBD therapeutic effects.
How They Did This
Systematic review of PubMed, PubMed Central, Cochrane Library, and Google Scholar for studies on cannabis and schizophrenia/psychosis published in the last 5 years. Quality assessment reduced 24 studies to 12 final inclusions.
Why This Research Matters
The opposing effects of THC and CBD on psychosis may explain why cannabis research has yielded contradictory findings. Separating these components could transform both risk assessment and treatment.
The Bigger Picture
The consistent finding that THC increases psychosis risk while CBD may reduce it has direct implications for cannabis product regulation. High-THC/low-CBD products, increasingly common in legal markets, may carry the greatest risk.
What This Study Doesn't Tell Us
Half the initial studies excluded for low quality; included studies were mostly reviews themselves (limited original data); small total evidence base (12 studies); did not quantify effect sizes.
Questions This Raises
- ?Would high-CBD/low-THC cannabis products carry less psychosis risk?
- ?Could CBD be developed as an adjunct treatment for schizophrenia?
Trust & Context
- Key Stat:
- 10 of 12 studies supported causal link; 6 supported CBD therapeutic effects
- Evidence Grade:
- Moderate: systematic methodology but many included studies were themselves reviews, and half of screened studies were excluded for low quality.
- Study Age:
- Published 2020.
- Original Title:
- The Association Between Cannabis Use and Schizophrenia: Causative or Curative? A Systematic Review.
- Published In:
- Cureus, 12(7), e9309 (2020)
- Authors:
- Patel, Shweta, Khan, Sahar, M, Saipavankumar, Hamid, Pousettef
- Database ID:
- RTHC-02773
Evidence Hierarchy
Analyzes all available research on a topic using a structured method.
What do these levels mean? →Frequently Asked Questions
Does cannabis cause schizophrenia?
This review found 10 of 12 studies supported a causal link, with THC identified as the primary risk component in genetically vulnerable individuals. However, the authors note the evidence is still not conclusive and more controlled studies are needed.
Can CBD help treat psychosis?
Six of 12 studies in this review supported therapeutic effects of CBD on psychotic symptoms. However, the data was described as minimal and further research on safety and efficacy is needed.
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Cite This Study
https://rethinkthc.com/research/RTHC-02773APA
Patel, Shweta; Khan, Sahar; M, Saipavankumar; Hamid, Pousettef. (2020). The Association Between Cannabis Use and Schizophrenia: Causative or Curative? A Systematic Review.. Cureus, 12(7), e9309. https://doi.org/10.7759/cureus.9309
MLA
Patel, Shweta, et al. "The Association Between Cannabis Use and Schizophrenia: Causative or Curative? A Systematic Review.." Cureus, 2020. https://doi.org/10.7759/cureus.9309
RethinkTHC
RethinkTHC Research Database. "The Association Between Cannabis Use and Schizophrenia: Caus..." RTHC-02773. Retrieved from https://rethinkthc.com/research/patel-2020-the-association-between-cannabis
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.