A systematic review of 8 high-quality studies found THC consistently linked to increased psychosis risk, while CBD showed potential therapeutic effects for schizophrenia symptoms—the two cannabinoids may work in opposite directions.
Psychiatrists advising patients about cannabis, schizophrenia researchers, policymakers considering cannabis product regulations, and cannabis users with psychosis concerns.
What the researchers found
The cannabis-schizophrenia relationship is one of the most polarized debates in psychiatric research. This systematic review cuts through the noise by applying rigorous quality filters to 112 initial records, ultimately including only 8 studies that met strict methodological standards.
The central finding: THC and CBD appear to push schizophrenia risk in opposite directions. THC is consistently associated with increased psychosis risk, while CBD has shown potential therapeutic effects on schizophrenia symptoms.
This dual nature of cannabis matters enormously for policy and clinical practice. Cannabis products vary wildly in their THC:CBD ratio—from high-THC concentrates with almost no CBD to CBD-dominant products with trace THC. Treating "cannabis" as a single entity obscures the fact that its two main components may have opposing effects on psychosis.
The review notes that approximately 20 million people worldwide are affected by schizophrenia, making the stakes of getting this right enormous. If THC increases risk while CBD potentially treats symptoms, then the composition of cannabis products—not just whether someone uses cannabis—becomes the critical variable.
The methodological rigor is a strength: the authors used AMSTAR 2, Cochrane Risk of Bias Tool, and Newcastle-Ottawa Scale to evaluate included studies, and only 8 of 112 screened records passed the quality threshold.
Why it matters
As cannabis becomes more accessible, distinguishing between THC-risk and CBD-benefit is essential for informed policy. Blanket statements that "cannabis causes psychosis" or "cannabis is safe" both miss the critical nuance. This review provides a framework for thinking about cannabis and schizophrenia that accounts for the distinct effects of different cannabinoids.
The numbers in context
~20 million people affected by schizophrenia globally. 112 records screened; 8 met inclusion criteria. THC associated with increased psychosis risk. CBD showed potential therapeutic effects for schizophrenia symptoms.
How the study worked
Systematic review per PRISMA 2020 guidelines. Searched PubMed, PubMed Central, Cochrane Library, and Google Scholar for peer-reviewed studies published 2017–2025. Quality assessment using AMSTAR 2, Cochrane Risk of Bias Tool, Newcastle-Ottawa Scale. 112 records screened; 8 high-quality studies included.
Who was studied
Eight high-quality studies analyzed, focusing on cannabis and schizophrenia.
What this study cannot tell us
Only 8 studies met inclusion criteria out of 112 screened—while this ensures quality, it limits the scope of conclusions. The strict 2017–2025 time window excludes earlier foundational research. The review can't resolve the causal question (does THC cause schizophrenia or do schizophrenia-prone individuals seek THC?). CBD's therapeutic potential is based on limited clinical evidence that needs more replication.
How to read the evidence
Systematic review with rigorous quality filtering—strong methodology though limited by the small number of studies meeting inclusion criteria.
When this study was published
Published in 2025 covering studies from 2017–2025, reflecting the most recent evidence on cannabis and psychosis.
The bigger picture
This adds important nuance to RTHC-00163's finding that the cannabis-psychosis link disappeared after adjusting for other substances, and to RTHC-00181's review showing mostly neutral population-level mental health effects from legalization. The THC/CBD distinction may resolve some of the contradictions in the literature: if rising THC potency (RTHC-00162) shifts the average cannabis product toward more psychosis risk, while CBD products move in the opposite direction, population-level studies might show net-neutral effects masking important subgroup dynamics.
Replication
Not stated in abstract.
Funding
Not reported in abstract.
Conflicts of interest
Not reported in abstract.
Questions still open
- Could CBD be developed as a standalone antipsychotic medication? Should cannabis products sold in legal markets be required to contain minimum CBD levels to offset THC's psychosis risk? Would genotyping for schizophrenia risk help identify who should avoid THC?
Read the original research
The Relationship Between Cannabis Use and Schizophrenia As a Risk Factor or For Its Therapeutic Potential: A Systematic Review of Evidence.
Cureus, 17(9), e92793
Cureus is a peer-reviewed open-access medical journal known for its focus on innovative research.
Citation
Rajput, Jaisingh; Narahari, Sandhya; Arif, Taha; Iftikhar, Rabiya; Arpan, Turimula; Tariq, Abdullah; Ali Duleh, Hamad Mohammad; Cherukuri, Sri Pranita. (2025). The Relationship Between Cannabis Use and Schizophrenia As a Risk Factor or For Its Therapeutic Potential: A Systematic Review of Evidence.. Cureus, 17(9), e92793. https://doi.org/10.7759/cureus.92793
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