The findings of an analysis published in the journal Clinical Psychology Review suggests that cannabis may potentially be an effective treatment for certain mental health disorders, and could even help people break free from serious drug addictions. 
Access to marijuana is growing. Cannabis is currently legal in some form in 29 U.S. states. And even despite marijuana being legalized for recreational use in a handful of states, it remains the most widely-used illicit drug in the United States.
But marijuana has proven to be an effective treatment for epilepsy (including rare forms of the seizure disorder) and has been shown to ease pain, prevent multiple sclerosis-related inflammation in the brain and spinal cord, and kill cancer cells. Cannabis has also been shown to be superior to drugs for Alzheimer’s disease.
Many marijuana users say the drug helps their depression, or post-traumatic stress disorder (PTSD), and theis review seems to back their claims.
Led by Zach Walsh, an associate professor of psychology at the University of British Columbia in Canada, the researchers conducted a systematic review of 60 studies assessing the effects of either medical or non-medical marijuana on mental health and substance abuse.
The findings were sort of a mixed bag. The team found that medical marijuana shows potential for treating post-traumatic stress disorder (PTSD), depression, and social anxiety.
“This is a substance that has potential use for mental health. We should be looking at it in the same way [as other drugs] and be holding it up to the same standard.” 
However, in people with psychotic disorders like bipolar disorder, the side effects may outweigh the benefits.
The review also indicated that marijuana could be a viable treatment for serious drug addiction, though more research is needed.
“We are really excited about the potential substitution effect. If people use cannabis as a replacement for opioid medications, or to get off of opioids or cut back, we could see some pretty dramatic public health benefits. The level of opioid overdoses is so high right now.”
The evidence to date suggests that medical marijuana causes only minor side effects, such as impaired short-term memory and temporary problems with cognitive function. Medical cannabis does not appear to raise the risk of self-harm or harm to others. 
But researchers face a major hurdle in studying the efficacy of marijuana in treating mental illness and drug addiction: The federal government refuses to reschedule marijuana. Right now, it’s a Schedule I drug, meaning the government does not recognize its medicinal value, and it has a high potential for abuse.
Researchers argue that rescheduling cannabis would also help eliminate the stigma associated with it, which would open the door to better studies.
“I think people will derive more benefit if they can speak more openly with providers about whether they are using cannabis and why.” 
Walsh envisions a “dream trial” that would compare whether people wanting to stop using opioids in favor of marijuana see better results than those who receive a marijuana placebo or those who try to quit with methadone or behavioral therapy. 
Even as we speak, Walsh is heading up a clinical trial of cannabis that is being funded by a medical marijuana producer, Tilray. Another researcher on the study has been a consultant for other medical cannabis producers. Walsh sees no conflict of interest, because it’s difficult to secure funding for marijuana-related research. He explained:
“I think we are entering a different world, but for now a lot of the research, at least in Canada [where Walsh is based], is funded by the producers.”