New analysis warns plan sponsors as evidence of mental health benefits lags rising medical cannabis use
Cannabis-based medicines are moving into drug plans, but the best available trials suggest they rarely help the mental health problems they are supposed to treat – and they add side‑effects.
According to a new systematic review and meta‑analysis in The Lancet Psychiatry, researchers analysed 54 randomised controlled trials of cannabinoids as primary treatment for mental disorders and substance‑use disorders, covering 2,477 participants from 1980 to May 2025.
The team, led by Jack Wilson at the University of Sydney’s Matilda Centre for Research in Mental Health and Substance Use, found little evidence that cannabis-based medicines improve core symptoms in most conditions studied.
Reuters reported that the review showed no significant benefit for several of the most common reasons people seek medical cannabis, including anxiety disorders, psychotic disorders, post‑traumatic stress disorder (PTSD) and opioid‑use disorder.
The same article noted that the authors found no randomised controlled trials at all for depression, highlighting a major hole in the evidence base.
As per CNN’s coverage of the research, Wilson said, “We found no evidence any form of cannabis is effective in treating anxiety, depression or post‑traumatic stress disorder, which are three of the leading reasons for which cannabis is prescribed.”
The products tested in these trials were mostly oral formulations such as capsules, sprays or oils, while in real‑world use many people rely on smoked cannabis, where evidence for benefit is even thinner.
Evidence of benefit was confined to a few narrow areas.
Reuters reported that a combination of cannabidiol (CBD) and delta‑9‑tetrahydrocannabinol (THC) was associated with reduced cannabis withdrawal symptoms and lower cannabis consumption among people with cannabis‑use disorder.
The Lancet Psychiatry article also found reduced tic severity in people with tic or Tourette’s syndrome, a reduction in autistic traits in autism spectrum disorder, and increased sleep time in insomnia when measured by electronic devices or sleep diaries.
Wilson told Reuters that the overall quality of evidence for autism and insomnia was low.
On safety, the Lancet Psychiatry paper found that cannabinoids increased the odds of all‑cause adverse events versus control, although serious adverse events and study withdrawals did not differ.
According to the article, common adverse events included dry mouth, nausea, diarrhoea and dizziness.
All of this sits against rapid growth in medical use.
Reuters noted that medical cannabinoids are now authorised in the US, Canada and Australia, and that many patients report using cannabis products to manage anxiety, PTSD and sleep problems.
CNN, citing survey data referenced by Wilson, reported that 27 percent of people aged 16 to 65 in the United States and Canada have used marijuana for medical purposes, with about half using it to manage their mental health.
CNN also highlighted broader risks that matter for long‑term disability exposure.
Experts interviewed by the network said regular use of potent marijuana during pregnancy, adolescence and young adulthood can interfere with brain development, and that heavy use among teens and young adults with mood disorders is linked to higher risks of self‑harm, suicide attempts and death.
CNN further reported that daily use of high‑potency cannabis may make a person up to six times more likely to develop a psychotic disorder such as schizophrenia or bipolar disorder compared with someone who has never used cannabis.
Rising potency and addiction risk add to the concern.
THC levels in cannabis have climbed from about 4 percent in the 1970s to averages of 18 percent–20 percent today, with some products at 35 percent and concentrates around 80 percent.
The same report, citing US public‑health data, said about three in ten people who use marijuana have cannabis use disorder, with withdrawal symptoms such as irritability, restlessness, mood and sleep difficulties, and appetite changes after quitting.
Against that backdrop, the alternatives look stronger.
CNN noted that selective serotonin reuptake inhibitors remain a standard pharmaceutical option for depression and anxiety, and that cognitive behavioural therapy is the leading psychotherapy, often combined with medication.
Wilson told Reuters that while “some people may experience legitimate benefits,” the overall evidence “is quite [not] there for the routine use of these medicines.”
