A major review has no mental health benefits of medicinal cannabis

a sign Lancet Psychiatry A paper published today – the largest review of the safety and efficacy of cannabinoids in a range of mental health conditions – found no evidence that medicinal cannabis is effective in treating depression, anxiety or post-traumatic stress disorder (PTSD).

The research comes amid more than a million prescription approvals and a tripling of sales of cannabinoid medicines (including both cannabidiol (CBD) and tetrahydrocannabinol (THC) products) in Australia over the past four years, often for the treatment of mental health and substance use disorders.

The study’s lead author, Dr Jack Wilson of the University of Sydney’s Matilda Centre, said the results called into question the approval of medicinal cannabis for the treatment of depression, anxiety and PTSD.

Although our paper did not specifically look at this, routine use of medicinal cannabis may do more harm than good by worsening mental health outcomes, for example increasing the risk of psychiatric symptoms and cannabis use disorder, and delaying the use of more effective treatments.

Dr Jack Wilson, University of Sydney’s Matilda Centre

More than 700,000 Australians have reported using medicinal cannabis to treat 250 different health conditions. Research has found evidence to suggest that medicinal cannabis may be useful for certain conditions – such as the treatment of cannabis use disorder (otherwise known as cannabis dependence), autism, insomnia, and tics or Tourette syndrome.

Dr Wilson said: “But the overall quality of evidence for these other conditions, such as autism and insomnia, was low. In the absence of strong medical or counseling support, the use of medicinal cannabis in these cases is rarely justified.

“However, there is evidence that medicinal cannabis may be beneficial in some health conditions, such as reducing some types of seizures, spasticity among people with multiple sclerosis, and managing some types of pain, but our research shows that the evidence for mental health disorders is lacking.

“Specifically in the case of autism, while studies have shown some evidence that medicinal cannabis can help reduce symptoms, it is worth noting that no one – or universal – experience autism, so this finding should be taken with caution.”

Research has found that medicinal cannabis is not effective for any substance abuse disorder. While medicinal cannabis may help with cannabis dependence, it has been found to increase cocaine cravings among people with cocaine use disorder.

“Since methadone is used to treat opioid use disorders, cannabis medications may be part of an effective treatment for those with cannabis use disorder. When administered in conjunction with psychotherapy, an oral formulation of cannabis has been shown to reduce smoking,” said Dr. Wilson.

He said, “However, when medicinal cannabis was used to treat people with cocaine use disorders, it increased their cravings. This means that it should not be considered for this purpose and may actually worsen cocaine dependence.”

Researchers are calling for more regulation for the prescription of medicinal cannabis

The rapid expansion in the use and prescribing rates of medicinal cannabis has raised concerns among major medical bodies, including the Australian Medical Association (AMA) and the Pharmacy Guild of Australia, about the largely unregulated growth in prescriptions and the uncertainty surrounding the efficacy and safety of these products.

In response, the Therapeutic Goods Administration (TGA) launched a review of its regulatory oversight of medicinal cannabis, with more than 500 responses published in February.

“Our study provides a comprehensive and independent assessment of the benefits and risks of medicinal cannabis, which may help the TGA and clinicians make evidence-based decisions, helping to ensure that patients receive effective treatment while minimizing harm from ineffective or unsafe cannabis products,” said Dr Wilson.

The systematic review and meta-analysis included the results of 54 randomized controlled trials (RCTs) published worldwide over a 45-year period (1980–2025).