Psychedelic treatments show promise for OCD while cannabis doesn’t, review finds

2025-12-13 16:00

A recent review of alternative treatments for obsessive compulsive disorder (OCD) indicates that psychedelic treatments show promise for the disorder while cannabis does not.

Dr Michael Van Ameringen, a psychiatry professor at McMaster University in Ontario, Canada and lead author of the review published in the Journal of Psychiatric Research, said that 40-60 % of OCD patients get either partial or no relief with available treatments, including SSRIs and exposure and response prevention therapy.

While psychedelics and cannabinoids have become part of the conversation surrounding OCD – a disorder characterized by intrusive, obsessive thoughts and/or compulsive behaviors – there is a much larger body of published evidence on the efficacy of these substances for more common conditions, like depression and anxiety.

“We wanted to hone down and really understand, is there evidence for these things that have been talked about to be used as the next step treatments?” Van Ameringen explained.

Given the paucity of existing literature, Van Ameringen said he didn’t know what to expect. To make up for the lack of published information, he included conference presentations and preliminary, unpublished findings in the review paper.

Upon compiling available evidence, Van Ameringen and his team found “stronger signals” for the efficacy of psychedelics, specifically psilocybin (the psychoactive component of “magic mushrooms,”) than for cannabinoids like THC and CBD.

Van Ameringen theorizes that the difference is related to how these substances interact with areas of the brain related to OCD. While cannabinoids activate the brain’s CB1 receptors, which regulate symptoms like compulsions and anxiety, available evidence shows they don’t offer lasting relief from OCD symptoms.

Psilocybin, on the other hand, can reduce connectivity in the brain’s default mode network, which “essentially is involved in self referential thinking and rumination. The default mode network is really activated in OCD”, he says.

A difference in the methodology of cannabis and psilocybin studies might also have contributed to the different results, says Dr Mohamed Sherif, a psychiatrist and computational neuroscientist at Brown University who will lead a future clinical trial on psilocybin for OCD. Psychedelic clinical trials, like the one Sherif is planning, tend to offer patients not only medication but also encouragement to frame their experience as a therapeutic “journey”.

“This was not done in cannabinoids [studies,]” Sherif explained.

Dr Terrence Ching, a clinical psychologist at the Yale School of Medicine, similarly wondered if the way people use cannabis versus psilocybin might explain the different outcomes. While people tend to use cannabis for temporary relief, psilocybin can help facilitate actual changes in the brain and in patients’ perception of their OCD.

“One could use cannabis for the same therapeutic reason, of confronting something deeper about their OCD or their obsessive fears. But conventionally, people tend to use cannabis for an avoidance function,” Ching explained.

Preliminary results from Ching’s clinical trial on a single dose of psilocybin for OCD were included in Van Ameringen’s review paper, and showed that psilocybin was effective for OCD symptoms compared to placebo. Ching is now preparing the results of the trial for publication, and planning a second clinical trial where OCD patients will receive two doses of psilocybin at different times.

During the single dose trial, 11 patients each received psilocybin or niacin, a placebo intended to mimic some of psilocybin’s effects so that patients would be unsure which drug they’d received. During dosing sessions, patients would sit with two facilitators who would offer minimal guidance in the form of open ended questions.

Ching said his protocol included strict rules about the type of touch that was allowed if patients requested it – only a hand on the shoulder or forearm – to create unambiguous ethical limits. Past psychedelic clinical trials have generated controversy when facilitators initiated unwanted touch with participants who were under the influence.

Ching said the trial was useful not only in showing that psychedelics can improve OCD symptoms, but also in revealing more about the nature of OCD, both for clinicians and for the participants themselves.

Psilocybin is known for inducing “mystical experiences”, characterized by a specific type and intensity of psychedelic effects, according to Ching.

“What we see in OCD is more often partial mystical experiences, people are kind of pumping the brakes when they have a sense that the psilocybin wants to take them into a deeper state of experiencing,” Ching said, adding that this highlights one of the core features of the disorder – the need to be in control.

While clinicians in psychedelic trials might typically encourage patients to go deeper, Ching said that with OCD patients, it’s important to remain “non-directive and non-judgemental”.

During the trial, Ching saw patients recognize their own resistance to the drug and gain deeper insight into their need for control, saying things like: “I really realize that this is how I’ve approached unknowable things in my life, but that’s what life is. Life is full of unknowable things.”

Ching is hopeful about the future of psychedelic medications, but there are several obstacles that make researching them difficult. Psilocybin is still an illegal schedule I substance in the US, which means that researchers must take additional steps to study it, including working with a DEA liaison and using a DEA approved safe that “needs to be bolted down to the ground”, in a private windowless room.

Researchers also must deal with the issue of “functional unblinding”, or the fact that psychedelic effects can mean trial participants are able to guess whether they received psilocybin or a placebo, which could alter their perception of their own symptoms. This is especially problematic given the hype around psychedelics, Ching said.

Many participants will enter a trial expecting a “miracle cure” – a narrative Ching believes is actually harmful to psychedelic research: “What we need to do now is to seriously, to treat psychedelics seriously, as any other worthwhile medication, to investigate in a controlled, rigorous way, in a way that is ethical, that pays homage to traditional Indigenous users of psychedelics, because there are, there is great wisdom there too.”