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Using medical or recreational marijuana to ease symptoms of numerous mental health conditions doesn’t work, according to two new analyses of existing gold-standard research.
Medical marijuana includes products with cannabidiol, or CBD, and delta-9-tetrahydrocannabinol, or THC, the part of the plant that produces euphoria.
“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,” 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 one of the studies published Monday in the journal Lancet Psychiatry, which analyzed results from 54 randomized controlled trials published between 1980 and 2025.
“The cannabis medications being administered in these studies were largely oral formulations, such as capsules, sprays or oils,” he said. “In real life, people typically use smoked cannabis, and there is even less evidence of its effectiveness for mental health.”
Using marijuana also did not improve other mental health conditions such as anorexia nervosa; bipolar disorder; obsessive-compulsive disorder, or OCD; or psychotic disorders such as schizophrenia, Wilson said.
Studies on marijuana are often small and can be difficult to conduct, experts say. Still, the randomized controlled trials that made up the Lancet review are the gold-standard of research, said Dr. Deepak Cyril D’Souza, Vikram Sodhi ’92 Professor of Psychiatry and director of the Yale Center for the Science of Cannabis and Cannabinoids in New Haven, Connecticut.
D’Souza, who was not involved in the Lancet study, is the senior author of a recent JAMA paper that also explored the effectiveness 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 US approves medical marijuana for mental health conditions.”
Dangers instead of benefits
While little evidence of benefit exists, the use of medical and recreational marijuana for mental health is growing, experts say. Some 27% of people between the ages of 16 and 65 in the United States and Canada have used marijuana for medical purposes, with “about half using it to manage their mental health,” Wilson said.
“Despite a lack of proof of efficacy, doctors continue to prescribe medical marijuana to treat mental health conditions,” he added. “In addition, the cannabis industry has connections with some of these studies, which is a conflict of interest that may impact the findings.”
Regular use of potent marijuana can be dangerous, experts say, especially to the most vulnerable. Utilizing marijuana during pregnancy, adolescence and young adulthood can interfere with brain development. Heavy use of marijuana by teens and young adults with mood disorders – such as depression and bipolar disorder – is linked to an increased risk of self-harm, suicide attempts and death.
In those individuals at high risk of bipolar or psychotic disorders, such as people with family histories, studies show the use of marijuana raises the risk of developing a psychotic or mental health disorder. Using it after the onset of a mental condition can worsen cognition and the chance of relapse.
“While there may be thousands, perhaps millions, of people who use cannabis sporadically, in very modest amounts and do not experience adverse events, we also know of people who used cannabis a few times and suffered catastrophic adverse events that altered the trajectory of their life forever,” D’Souza said.
“If you are a daily user of high potency cannabis, for example, you may be six times more likely to develop a psychotic disorder such as schizophrenia or bipolar disorder than somebody who’s never used cannabis,” he said.
Today’s weed is more powerful and addictive
Contributing to the problem: The amount of THC in today’s marijuana has skyrocketed from approximately 4% in the 1970s to an average of 18% to 20% today, D’Souza said.
“You can now buy cannabis in dispensaries that has a THC content of 35%,” he said. “Marijuana concentrates, which are similar to nicotine concentrates, have a THC content of 80%. That’s about 20 times greater than the THC content of cannabis from the 1960s and ’70s.”
High potency weed is contributing to a rise in addiction as well. In the United States, about 3 in 10 people who use marijuana have cannabis use disorder, the medical term for marijuana addiction, according to the US Centers for Disease and Prevention.
Cannabis use disorder, also known as marijuana use disorder, is associated with dependence on the use of weed. People are considered dependent on weed when they feel food cravings or have a lack of appetite, irritability, restlessness, and mood and sleep difficulties after quitting, according to the National Institute on Drug Abuse.
Where to turn instead of marijuana
There are proven methods to treat mental health concerns, experts say. Selective serotonin reuptake inhibitors, known as SSRIs, are a common pharmaceutical approach for depression and anxiety.
The leading psychotherapy for these conditions is cognitive behavioral therapy, or CBT, which is often combined with SSRIs. Cognitive behavior therapy is goal-oriented and focuses on changing negative thoughts and behaviors to improve emotional regulation and mood.
The Association for Behavioral and Cognitive Therapies has a listing of therapists who are CBT-trained that is searchable by zip code. The American Psychological Association also lists CBT-trained therapists under “treatment methods” in its “Find a Psychologist” tool.
