The randomized trial evidence for cannabis treating mental health conditions is thin and mixed — CBD shows some anxiety promise, but THC-containing products have more risk than benefit for most psychiatric conditions.
Anyone considering cannabis for anxiety, depression, PTSD, or substance use issues; clinicians prescribing medical cannabis for psychiatric conditions; researchers designing future trials.
What the researchers found
This scoping review mapped all available randomized controlled trial evidence on medicinal cannabis for mental health conditions classified by the DSM-5. The researchers found an emerging but highly heterogeneous evidence base.
CBD showed the most consistent signal for anxiety-related conditions, with some trials reporting reductions in subjective anxiety measures. For PTSD, a small number of trials suggested potential benefit from THC-containing products, but results were mixed and trial quality was variable.
For depression, the evidence was particularly thin — few trials directly targeted depression as a primary outcome, and those that did showed inconsistent results. For substance use disorders, some trials explored cannabinoids as substitution or harm reduction tools, but the evidence remained inconclusive.
Across conditions, the review highlighted a fundamental challenge: high heterogeneity in cannabis product types, dosing, duration, and outcome measures made it difficult to draw firm conclusions about any single condition.
Why it matters
Global prescribing of medicinal cannabis is increasing, often outpacing the evidence base — particularly for mental health conditions. While cannabis has established evidence for conditions like epilepsy and multiple sclerosis spasticity, this review shows that the psychiatric evidence is far less developed, creating a gap between clinical practice and what trials actually demonstrate.
The numbers in context
Review covered all available RCTs for cannabis and mental health conditions through the search period. Conditions examined included anxiety disorders, PTSD, depression, and substance use disorders. Specific trial counts and sample sizes varied by condition.
How the study worked
Scoping review following established methodological frameworks (likely PRISMA-ScR). Searched for randomized controlled trials investigating medicinal cannabis for any mental health condition classified in the DSM-5. Assessed efficacy through clinical outcomes and safety through adverse events and treatment withdrawals.
Who was studied
28 RCTs across 12 DSM-5 mental health conditions, sample sizes ranged from 6 to 150 participants.
What this study cannot tell us
As a scoping review rather than a systematic review with meta-analysis, this maps the landscape without pooling effect sizes. The high heterogeneity across studies — different products, doses, durations, and outcome measures — limits the ability to make definitive statements. Publication bias may also affect the available evidence.
How to read the evidence
Scoping review of randomized controlled trials — captures the breadth of available high-quality evidence but the underlying trials vary considerably in size and quality.
When this study was published
Published in 2026, providing the most current mapping of cannabis clinical trial evidence for mental health conditions.
The bigger picture
This review sits at the intersection of two trends: rising medicinal cannabis prescribing and growing recognition that mental health treatment needs better options. The tension is that patient demand and policy liberalization are moving faster than the clinical trial infrastructure can generate reliable answers. The findings connect to the broader anxiety literature (RTHC-00053, RTHC-00235) and the substance use treatment research (RTHC-00202, RTHC-00210) in this database.
Replication
Not stated in abstract.
Funding
Not reported in abstract.
Conflicts of interest
Not reported in abstract.
Questions still open
- Which specific mental health conditions have the strongest case for further cannabis clinical trials? Can standardization of cannabis products and outcome measures make future trials more comparable? How should clinicians counsel patients who want to use cannabis for mental health conditions when the trial evidence is this limited?
Read the original research
Randomised Controlled Trial Evidence on Medicinal Cannabis for Treatment of Mental Health and Substance Use Disorders: A Scoping Review.
Clinical drug investigation, 46(1), 5-36
Clinical Drug Investigation is a peer-reviewed journal focused on clinical research in drug development and evaluation.
Citation
Cooling, Sophie; Bonomo, Yvonne Ann; Castle, David; Hallinan, Christine Mary. (2026). Randomised Controlled Trial Evidence on Medicinal Cannabis for Treatment of Mental Health and Substance Use Disorders: A Scoping Review.. Clinical drug investigation, 46(1), 5-36. https://doi.org/10.1007/s40261-025-01501-3
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