‘No evidence’ cannabis works for most mental health disorders: Review

A major review of medicinal cannabis clinical trials has found no evidence of its efficacy in treating a range of mental health disorders, including depression, anxiety and post-traumatic stress disorder (PTSD).

The systematic review and meta-analysis, published in The Lancet Psychiatry, looked at 54 randomised controlled trials from 1980 to 2025 involving 2477 participants.
 
In what authors describe as ‘the largest-ever review of the safety and efficacy of cannabinoids across a range of mental health conditions’, they found no evidence for medicinal cannabis as an effective treatment for anxiety, depression or PTSD.
 
However, they did find some potential benefits for treating conditions such as cannabis use disorder, autism, insomnia, and tics or Tourette’s syndrome.
 
The authors also noted the absence of randomised controlled trials in assessing it for depression treatment.
 
‘Cannabinoids are increasingly being authorised for the treatment of mental disorders and substance use disorders, yet our review shows little evidence of efficacy,’ they wrote.
 
‘It is concerning that the use of these treatments could delay or replace the use of more effective therapies.
 
‘There is a crucial need for improved study design that includes larger and more representative participant samples.’
 
Associate Professor Vicki Kotsirilos, a Melbourne GP and one of the first authorised medicinal cannabis prescribers in Australia, described the findings as ‘significant’.
 
‘This is the most comprehensive study to date found in the literature and should help set up clinical guidance for health practitioners when choosing to prescribe medicinal cannabis,’ she told newsGP.  
 
‘The most significant findings of relevance are that no research suggests medicinal cannabis is effective for treating mental health conditions such as depression, anxiety, PTSD, anorexia nervosa, cocaine abuse disorder, attention deficit hyperactivity disorder, and obsessive-compulsive disorder.’
 
It comes as a major review of medicinal cannabis regulation is taking place in Australia, following skyrocketing prescriptions of unapproved products in recent years.
 
The Therapeutic Goods Administration (TGA), which is carrying out the review, reports anxiety as one of the most common reasons for prescribing high potency tetrahydrocannabinol (THC) products in Australia, second only to pain.
 
‘This is a concern especially if there is no research to support the use of medicinal cannabis for anxiety,’ Associate Professor Kotsirilos said.
 
‘We know from research that THC can cause anxiety, may lead to cannabis use disorder, and mental health issues such as psychosis in sensitive people.
 
‘So, there needs to be an urgent assessment of prescribing trends in Australia.
 
‘It is worth reminding ourselves that unapproved medicinal cannabis is a last-resort treatment for any condition, and there are effective evidence-based non-pharmacological treatments such as cognitive behaviour therapy, mindfulness, counselling, exercise, stress management, and pharmacological treatments that may assist with anxiety.’
 
RACGP President Dr Michael Wright said while medicinal cannabis may have a role for a small number of patients, ‘there are very few clinical indications for its use’.
 
‘In most cases, there are alternative evidence‑based therapies which remain more appropriate, effective, and better understood,’ he said.
 
Dr Wright also expressed concerns about the huge growth in medicinal cannabis prescribing, particularly from single‑issue prescribers.
 
‘This trend risks undermining clinical standards, fragmenting care, and exposing patients to treatments where the evidence base remains limited,’ he said.
 
‘Given these concerns, the RACGP believes the TGA must take a strong and active role in its current review, ensuring prescribing is grounded in robust evidence, appropriate safeguards are in place, and patient safety remains paramount.
 
‘Medicinal cannabis should be treated like any other medicine, prescribed judiciously, monitored carefully, and integrated into holistic, GP‑led care.’
 
Lead author Dr Jack Wilson from the University of Sydney’s Matilda Centre noted the potential benefits of medicinal cannabis for treating cannabis use disorder, autism, insomnia, and tics or Tourette’s syndrome.
 
However, he warned that the quality of evidence for conditions such as autism and insomnia is low.
 
‘In the absence of robust medical or counselling support, the use of medicinal cannabis in these cases [is] rarely justified,’ he said.
 
‘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.’
 
Associate Professor Kotsirilos said evidence suggesting medicinal cannabis may be helpful for some conditions is important when establishing clinical guidelines.
 
‘It means medicinal cannabis may be a useful consideration if there are no contraindications in conditions when all other evidence-based treatments have failed,’ she said.
 
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medicinal cannabis mental health disorders substance use disorders