No evidence cannabis helps anxiety, depression, or PTSD

Recorded: March 21, 2026, 10 p.m.

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Huge study finds no evidence cannabis helps anxiety, depression, or PTSD | ScienceDaily

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Huge study finds no evidence cannabis helps anxiety, depression, or PTSD

Date:
March 20, 2026
Source:
University of Sydney
Summary:
The largest review of medicinal cannabis to date found it doesn’t effectively treat anxiety, depression, or PTSD—despite millions using it for those reasons. Researchers warn it could even make mental health worse, raising risks like psychosis and addiction while delaying proven treatments. Some limited benefits were seen for conditions like insomnia and autism, but the evidence is weak. The findings are fueling calls for stricter oversight as cannabis use continues to rise.
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FULL STORY

A sweeping new analysis finds medicinal cannabis doesn’t work for anxiety, depression, or PTSD—and may even make mental health worse. Credit: Shutterstock

A major paper published in The Lancet reports that medicinal cannabis does not effectively treat anxiety, depression, or post-traumatic stress disorder (PTSD). The analysis is the largest to date examining both the safety and effectiveness of cannabinoids across a wide range of mental health conditions.

These findings arrive at a time when cannabis use for medical purposes is widespread. About 27 percent of people aged 16-65 in the United States and Canada report using cannabis medically, and roughly half of them say they use it to manage mental health symptoms.
Lead author Dr. Jack Wilson from the University of Sydney's Matilda Centre said the results raise serious questions about approving medicinal cannabis for conditions like anxiety, depression, and PTSD.
"Though our paper didn't specifically look at this, the routine use of medicinal cannabis could be doing more harm than good by worsening mental health outcomes, for example a greater risk of psychotic symptoms and developing cannabis use disorder, and delaying the use of more effective treatments," he said.
Limited Evidence for Other Conditions
The researchers did find some indications that medicinal cannabis might help in certain cases. These include cannabis use disorder (otherwise known as cannabis dependency), autism, insomnia, and tics or Tourette's syndrome.
However, Dr. Wilson emphasized that the supporting evidence for these uses is not strong.

"But the overall quality of evidence for these other conditions, such as autism and insomnia, was low. In the absence of robust medical or counseling support, the use of medicinal cannabis in these cases are rarely justified.
"There is, however, evidence that medicinal cannabis may be beneficial in certain health conditions, such as reducing seizures associated with some forms of epilepsy, spasticity among those with multiple sclerosis, and managing certain types of pain, but our study shows the evidence for mental health disorders falls short.
"In the case of autism specifically, while the study showed some evidence medicinal cannabis could assist with a reduction in symptoms, it is worth noting that there is no one -- or universal -- experience of autism, so this finding should be treated with caution."
Mixed Results for Substance Use Disorders
The review also looked at how medicinal cannabis affects different substance use disorders. Results varied depending on the condition.
Cannabis-based treatments showed some potential for helping people with cannabis dependence. However, the study found a concerning effect in people with cocaine-use disorder, where cannabis use increased cravings.

"Similar to how methadone is used to treat opioid-use disorder, cannabis medicines may form part of an effective treatment for those with a cannabis-use disorder. When administered alongside psychological therapy, an oral formulation of cannabis was shown to reduce cannabis smoking," Dr. Wilson said.
"However, when medicinal cannabis was used to treat people with cocaine-use disorder, it increased their cravings. This means it should not be considered for this purpose and may, in fact, worsen cocaine dependence," he said.
Calls for Stronger Regulation of Medicinal Cannabis
The rapid rise in medicinal cannabis use and prescribing has raised concerns among major medical organizations, including the American Medical Association. Experts point to limited regulation and ongoing uncertainty about how effective and safe these products really are.
"Our study provides a comprehensive and independent assessment of the benefits and risks of cannabis medicines, which may support clinicians to make evidence-based decisions, helping to ensure patients receive effective treatments while minimising harm from ineffective or unsafe cannabis products," Dr. Wilson said.
Large Global Analysis Spanning 45 Years
The findings are based on a systematic review and meta-analysis of 54 randomized controlled trials (RCTs) conducted worldwide over a 45 year period (1980-2025).
The research was funded by the NHMRC. Wayne Hall and Myfanwy Graham have received consultation fees from the World Health Organization. Wayne Hall has received payment for expert testimony on the risks of cannabis use. Myfanwy Graham is an appropriate member of the Medicinal Cannabis Expert Working Group, Australian Department of Health, Ageing and Disability. Myfanwy Graham has also received funding from the Therapeutic Goods Administration for independent evidence reviews on medicinal cannabis. All other authors declare no competing interests.

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The University of Sydney’s recent, expansive study, published in The Lancet Psychiatry, presents a definitive challenge to the widespread utilization of medicinal cannabis for treating anxiety, depression, or post-traumatic stress disorder (PTSD). This analysis, the largest to date examining cannabinoid efficacy across a broad spectrum of mental health conditions, reveals a stark absence of evidence supporting its effectiveness, and, crucially, suggests it may potentially exacerbate these ailments. The research, spanning 45 years and incorporating data from 54 randomized controlled trials, strongly indicates that routine medicinal cannabis use does not provide a reliable therapeutic benefit for these complex conditions; instead, it carries the risk of intensifying symptoms such as psychosis and cannabis use disorder, thereby delaying access to established and confirmed treatments.

Dr. Jack Wilson, the study’s lead author, highlighted the critical concern that the current reliance on medicinal cannabis may inadvertently worsen mental health outcomes. The investigation did identify limited, albeit weak, evidence suggesting a possible benefit in conditions like cannabis use disorder, autism, insomnia, and tics/Tourette’s syndrome. However, Wilson emphasized that the quality of evidence surrounding these alternative applications was low, and that the use of cannabis in these instances is primarily justified only in the absence of robust, medically supported therapies. The study acknowledges some limited successes with conditions like epilepsy, multiple sclerosis, and pain management, but consistently underscores the dearth of evidence concerning mental health disorders. Specifically, the findings regarding autism highlighted the variability of the condition, necessitating a cautious approach to interpreting the observed symptom reduction.

Furthermore, the research explored the effects of medicinal cannabis on substance use disorders, revealing a nuanced and concerning dynamic. While cannabis-based treatments exhibited some potential in addressing cannabis dependence, a disconcerting trend emerged with cocaine-use disorder, where cannabis was found to intensify cravings. Dr. Wilson underscored the dangers of utilizing cannabis medicines in this context, advocating that it should not be considered a treatment option and may instead exacerbate cocaine dependence. The study’s findings contribute to a broader discussion about regulations, particularly regarding the increasing use of cannabis, and the need for transparent assessments of its efficacy and safety. The analysis ultimately fuels a call for stricter oversight, aligning its conclusions with concerns raised by organizations like the American Medical Association, which have expressed anxieties regarding the unregulated proliferation of medicinal cannabis products and the resulting uncertainties surrounding their impact. The research serves as an important, independent evaluation of the benefits and hazards of cannabinoids, intended to guide clinicians in making evidence-based decisions, ensuring patient safety and minimizing the harm associated with ineffective or unsafe cannabis products.