Thirty-eight states plus the District of Columbia allow practitioners to recommend medical marijuana for post-traumatic stress disorder.
But what if they’re all wrong? A new systematic review of results from randomized controlled trials involving marijuana suggests they are.
The review doesn’t surprise me. Both the scientific and the anecdotal evidence stand clearly against the use of this drug as a mental health treatment. Indeed, I believe it’s more likely to do harm than good. As the CEO of a group that advocates for science-based drug policy, I spend a huge amount of time working with individuals and families harmed by marijuana. Marijuana is far more dangerous than commonly understood, especially today’s ultra-high-potency products. And while many advocates of medical marijuana are motivated by genuine compassion for the sick, the increasing normalization of marijuana use over the past three decades has been a public health disaster.
The new review appears in the April issue of Lancet Psychiatry. It takes in some 45 years of randomized controlled trials on the efficacy of marijuana for mental health issues like PTSD as well as substance abuse disorders: a total of 54 trials with close to 2,500 participants.
Its central finding? “There were no significant effects on outcomes associated with anxiety, anorexia nervosa, psychotic disorders, post-traumatic stress disorder, and opioid use disorder,” the authors write in the paper. The lead author told the press they “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.”
This should not come as a surprise. Rigorously derived evidence for the medical efficacy of marijuana is thin and states creating medical programs was primarily a political move, decided at various ballot boxes.
The wider literature broadly supports The Lancet findings. Take two recent publications as a representative selection.
One is a Cochrane review, published in January, that examined the literature on THC efficacy in treating chronic pain – another condition for which medical marijuana is frequently recommended. The review found “no clear evidence” for THC’s effect in achieving significant pain relief.
The second is another systematic review, which appeared in JAMA in November. Led by researchers at UCLA, UCSF, and NYU, the review concluded, “Evidence from randomized clinical trials does not support the use of cannabis or cannabinoids for most conditions for which it is promoted, such as acute pain and insomnia.” The study’s lead author, Michael Hsu, noted in a press release: “While many people turn to cannabis seeking relief, our review highlights significant gaps between public perception and scientific evidence regarding its effectiveness for most medical conditions.”
And while renewed public attention to these issues is welcome, my work has kept me long acquainted with the fact that these concerns are not novel. While there is little to no meaningful evidence for the therapeutic potential of marijuana (outside FDA-approved drugs derived from it, like Marinol and Epidiolex), the evidence for its mental health harms is overwhelming.
A major study in JAMA Health Forum published in February found that past-year cannabis use was associated with a more than double the risk of incident psychotic as well as bipolar disorders, a 34% higher risk of depressive disorder, and a 24% higher risk of anxiety disorders later in life. A Canadian study, also from February, found that people with cannabis-use disorder (CUD) developed schizophrenia more than 12 times as frequently as those with no CUD, even as overall schizophrenia rates stayed stable over time.
A January study from Mass General Brigham hospital researchers found that after commercialization in Massachusetts, rates of marijuana use and marijuana-related disorders disproportionately increased among adolescents who arrived in the ER with a psychiatric emergency. In 2023, a Danish study covering the health data of almost 7 million found that cannabis use disorder was associated with as much as 30% of schizophrenia cases among young men. Another 2023 study, from Columbia University, found that teens with non-disordered marijuana use (i.e., not addicts) had approximately two to four times greater odds of exhibiting mental health issues. A 2019 study from The Lancet found an almost fivefold increase in the risk factor for psychotic disorder among daily marijuana users.
None of this is should be surprising – we’ve known about this connection for decades. A 1987 study from The Lancet, using Swedish data, found that the relative risk for schizophrenia among high consumers of cannabis (defined as use on more than fifty occasions) was sixfold what it was for non-users.
The story these data tell – and have long been telling – is not that marijuana has undiscovered potential blocked by federal policy. On the contrary, the best evidence we have suggests marijuana harms more than it helps.
I have spent years following the science that undercuts the effort to make marijuana into something it simply isn’t. I’ve spent years trying to mitigate the human fallout of that campaign: broken families, damaged users, increased rates of addiction. The fact that our national media has become increasingly focused on this side of the story is heartening. Witness The New York Times’ recent and significant revision of its previous position on the risks of legal marijuana, admitting that wide access and strong normalization have degraded public health.
The same states that created medical marijuana programs in order to help sick people with no other options must start following the science here as well. Otherwise, those truly suffering – be it from PTSD, chronic pain, depression, or anything else – will be chasing a mirage.
Kevin A. Sabet is the CEO of Smart Approaches to Marijuana. He holds a Ph.D. in social policy from Oxford and is on the adjunct faculty at the Yale School of Medicine.
