Recent comprehensive reviews of clinical trials have concluded that there is limited high-quality evidence to support the effectiveness of medicinal cannabis for treating most mental health conditions, including anxiety, depression, and post-traumatic stress disorder (PTSD). Despite this, the use of cannabis-based products for mental health concerns has been increasing globally, prompting calls for more rigorous research and regulatory oversight.
Key Findings from Major Reviews
A significant review published in The Lancet Psychiatry, which analyzed 54 randomized controlled trials involving 2,477 participants from 1980 to 2025, found no evidence that any form of cannabis is effective in treating anxiety, depression, or PTSD. This review, led by Jack Wilson from the University of Sydney, also indicated no significant evidence for its effectiveness in conditions such as anorexia nervosa, bipolar disorder, obsessive-compulsive disorder (OCD), or psychotic disorders like schizophrenia.
"No evidence that any form of cannabis is effective in treating anxiety, depression, or PTSD."
A separate review published in JAMA Internal Medicine reached similar conclusions, additionally warning of "substantial risks" for vulnerable populations.
Conditions with Limited or Low-Quality Evidence of Potential Benefit
While the overall evidence for most mental health conditions was insufficient, the reviews identified some areas with limited or low-quality evidence of potential benefits:
- Cannabis-use disorder: A combination of cannabidiol (CBD) and THC was associated with reduced cannabis withdrawal symptoms and lower cannabis consumption in some individuals.
- Tourette's syndrome: Cannabinoids were linked to reductions in tic severity.
- Insomnia: Increased sleep time was observed in patients treated with cannabis medicines.
- Autism spectrum disorder: Reductions in some autistic traits were reported, although the quality of evidence for autism and insomnia was deemed low by researchers.
Notably, researchers reported no randomized controlled trials evaluating cannabinoids specifically for depression. The cannabis medications studied were largely oral formulations, such as capsules, sprays, or oils, with less evidence for the effectiveness of smoked cannabis for mental health.
Disparity Between Prescribing Patterns and Research
In countries like Australia, medicinal cannabis, particularly products with higher levels of THC, is commonly prescribed for mental health conditions, often for anxiety, depression, and PTSD among men aged 18 to 44. Approvals for high-THC products for anxiety are nearly three times more frequent than for CBD-only products, despite most high-quality clinical trials for anxiety focusing on CBD-based treatments. This pattern highlights a significant disparity between public cannabis use for medical purposes and available scientific data.
Over one million Australians have used medicinal cannabis, primarily in the last five years, with mental health management frequently cited as a reason. The Australian Therapeutic Goods Administration (TGA) has not approved over 99% of medicinal cannabis products prescribed in Australia.
Safety and Risks
Experts and regulatory bodies have raised significant concerns about the potential risks associated with medicinal cannabis, particularly products with higher THC levels:
- Psychosis: Emerging evidence indicates psychosis has been reported among individuals using medicinal cannabis with higher THC levels. The TGA advises against THC-containing products for those with a personal or family history of psychosis or schizophrenia and cautions use in people with current or past mood or anxiety disorders. Daily or near-daily cannabis use is linked to a higher risk of psychosis or may contribute to its development.
- Brain Development: Use during pregnancy, adolescence, and young adulthood can interfere with crucial brain development.
- Mental Health Worsening: For individuals with existing mood disorders, heavy use by teens and young adults is linked to an increased risk of self-harm, suicide attempts, and death. Using cannabis after the onset of a mental condition may worsen cognition and increase the chance of relapse.
- Addiction and Withdrawal: Approximately one in three or four medicinal cannabis users may develop cannabis dependence and experience withdrawal symptoms if use is stopped suddenly. These can include increased anxiety, sleep difficulties, irritability, and restlessness. The US Centers for Disease Control and Prevention report that about 3 in 10 marijuana users have cannabis use disorder.
- THC Potency: The amount of delta-9-tetrahydrocannabinol (THC), the psychoactive component, has increased significantly over decades, from about 4% in the 1970s to an average of 18% to 20% today, with some products reaching 35% or more. This increased potency is linked to increased mental health risks and a rise in addiction.
Some individuals interpret increased mental health symptoms upon discontinuing medicinal cannabis as evidence of its prior efficacy, but these symptoms may be due to cannabis withdrawal.
Calls for Further Research and Regulation
Given the conflicting and low-quality evidence, researchers and medical bodies, including the Australian Medical Association (AMA), state that medicinal cannabis is not strongly recommended as the best treatment for most mental health conditions.
The AMA emphasizes the necessity for more robust regulatory oversight and stronger prescribing safeguards, advocating for medicinal cannabis to undergo the same rigorous safety, quality, and efficacy trials as other medicines and be registered on the Australian Register of Therapeutic Goods (ARTG).
The Australian Health Practitioner Regulation Agency (AHPRA) advises doctors to prescribe cannabis sparingly, as a last resort. Experts emphasize the need for more high-quality trials with larger and more representative samples to clarify the therapeutic role of cannabinoids, especially for conditions with limited alternative treatments.
Proven Alternatives for Mental Health
Medical professionals recommend that individuals, particularly those with a history of mental health concerns, consult with a medical professional to evaluate potential benefits and risks.
Proven methods are available for treating mental health concerns, including:
- Pharmaceutical approaches such as Selective Serotonin Reuptake Inhibitors (SSRIs) for depression and anxiety.
- Psychotherapies like Cognitive Behavioral Therapy (CBT), which aims to modify negative thoughts and behaviors.