Using medical or recreational marijuana to ease symptoms of mental health conditions does not work, according to two new analyses of existing gold-standard research.
Medical marijuana includes products containing cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC), the compound responsible for marijuana’s euphoric effects.
“We found no evidence that any form of cannabis is effective in treating anxiety, depression or post-traumatic stress disorder, which are three of the leading reasons cannabis is prescribed,” said Jack Wilson, a postdoctoral research fellow at the University of Sydney’s Matilda Centre for Research in Mental Health and Substance Use.
Wilson is the lead author of a study published Monday in Lancet Psychiatry that analyzed 54 randomized controlled trials conducted between 1980 and 2025.
“The cannabis medications used in these studies were largely oral formulations such as capsules, sprays or oils,” Wilson said. “In real life, people typically use smoked cannabis, and there is even less evidence of its effectiveness for mental health.”
Researchers also found no improvement in other mental health conditions, including anorexia nervosa, bipolar disorder, obsessive-compulsive disorder and psychotic disorders such as schizophrenia.
Randomized controlled trials are considered the gold standard of research, said Dr. Deepak Cyril D’Souza, professor of psychiatry and director of the Yale Center for the Science of Cannabis and Cannabinoids. D’Souza, who was not involved in the Lancet study, recently co-authored a separate paper in JAMA examining the effects of natural and synthetic forms of CBD and THC on mental health conditions.
“These two papers clearly show there isn’t any evidence to recommend the use of cannabis or cannabis derivatives to treat mental health,” D’Souza said. “Yet almost every state in the U.S. approves medical marijuana for mental health conditions.”
Dangers Instead of Benefits
Despite the lack of evidence, marijuana use for mental health continues to grow. About 27% of people ages 16 to 65 in the United States and Canada report using marijuana for medical purposes, with roughly half saying they use it to manage mental health concerns, Wilson said.
Experts warn that regular use of potent marijuana can be risky, particularly for vulnerable groups. Using marijuana during pregnancy, adolescence or young adulthood may interfere with brain development.
Heavy use among teens and young adults with mood disorders — such as depression or bipolar disorder — has been linked to a higher risk of self-harm, suicide attempts and death.
Research also shows that people with a family history of bipolar or psychotic disorders face a greater chance of developing those conditions if they use marijuana. For people already diagnosed with mental illness, marijuana use can worsen cognition and increase the likelihood of relapse.
“While many people may use cannabis occasionally without problems, we also know of people who used it a few times and experienced severe adverse events that changed the course of their lives,” D’Souza said.
Daily users of high-potency cannabis may be six times more likely to develop psychotic disorders such as schizophrenia or bipolar disorder compared with those who have never used it.
Stronger Marijuana, Rising Addiction
Today’s marijuana is far more potent than in past decades. THC levels have increased from about 4% in the 1970s to an average of 18% to 20% today, with some dispensary products reaching 35%. Marijuana concentrates can contain THC levels as high as 80%.
Higher potency is also linked to addiction. In the United States, about three in ten marijuana users develop cannabis use disorder, according to the Centers for Disease Control and Prevention.
Proven Treatments
Experts say there are proven treatments for mental health conditions. Selective serotonin reuptake inhibitors, or SSRIs, are commonly prescribed medications for anxiety and depression.
Psychotherapy — especially cognitive behavioral therapy (CBT) — is also widely used. CBT focuses on identifying and changing negative thought patterns and behaviors to improve mood and emotional regulation.
Resources for finding CBT-trained therapists are available through organizations such as the Association for Behavioral and Cognitive Therapies and the American Psychological Association.