Cannabis-based medications are often used to treat mental health problems, but a new review suggests they may not work as well as many people hope.

Researchers looked at decades of studies and found little evidence that cannabis helps with most mental health or substance-use disorders.

The findings come from a review — published March 16 in The Lancet — of 54 randomized clinical trials involving 2,477 people. The studies were conducted between 1980 and May 2025.

Cannabis products are widely used in countries like the U.S., Canada and Australia. Many people turn to them for conditions such as anxiety, post-traumatic stress disorder (PTSD) and sleep problems.

But when researchers reviewed the data, they did not find strong proof that these treatments help with many of those conditions.

“Some people may experience legitimate benefits, and that's great,” lead author Jack Wilson, a postdoctoral reserach fellow at the University of Sydney, told KSL. "But when we look at the evidence as a whole, we just don't see that the evidence is quite there for the routine use of these medicines."

The review found no meaningful improvement for several widely treated conditions, including:

• Anxiety disorders

• Psychotic disorders

• PTSD

• Opioid-use disorder

Researchers also found no randomized trials at all evaluating cannabis for depression.

The study did find some promise for certain conditions, however.

A mix of CBD and THC, the main compounds in cannabis, was linked to reduced withdrawal symptoms and lower use in people with cannabis-use disorder.

There was also some evidence that cannabinoids may help:

• Reduce tics in people with Tourette’s syndrome

• Improve sleep in people with insomnia

• Reduce certain traits linked to autism

But researchers said the evidence for these benefits was low.

As the use of medical cannabis grows, researchers said better studies are needed to understand when, and if, it truly helps.

“We clearly need to do more research on medical cannabis, particularly for those conditions that have limited alternative treatments,” Wilson said.