New Study Investigates Cannabidiol (CBD) for Psychosis

A new study examines the effects of CBD as an adjunct therapy to antipsychotic medication for patients diagnosed with schizophrenia.

Jessica Janze

A new study, published in The American Journal of Psychiatry, investigates potential antipsychotic properties of cannabidiol (CBD) in patients with schizophrenia. The results of the randomized, placebo-controlled study indicate CBD may lower positive psychotic symptoms and improve cognitive performance and overall functioning. Patients who received CBD, versus the placebo, were more likely to be rated as improved by their treating clinician.

“Although the magnitude of the effect on positive symptoms was modest, it was seen in patients who were already being treated with antipsychotic medication at appropriate dosages; the improvement was thus over and above the effect of antipsychotic treatment,” the researchers, led by Philip McGuire at King’s College London, write.

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While antipsychotic medication is typically recommended as the first line of treatment for individuals with schizophrenia, the long term effectiveness have been challenged. When an individual is responsive to medication, it is mainly reflected in reduced positive psychotic symptoms (referring to the presence of odd or usual feelings, thoughts, or behaviors). Non-pharmaceutical treatments, such as lifestyle change and mental health counseling, are effective for individuals diagnosed with schizophrenia and other psychotic disorders as well.

Research investigating the effects of CBD is in its infancy but has shown promise in reducing psychotic symptoms in patients with Parkinson’s disease. In healthy volunteers, CBD has demonstrated the opposite effects of delta-9-tetrahydrocannabinol (THC) on brain functioning and has been found to reduce anxiety, paranoid symptoms, and memory impairment.

In the first ever placebo-controlled trial of CBD in people diagnosed with schizophrenia, McGuire and collogues investigate the effectiveness and safety of CBD used as an adjunct to antipsychotic medications. Eighty-three patients with a diagnosis of schizophrenia or similar psychotic disorders participated in the 8-week, double-blind, and parallel-group trial at 15 hospitals across the U.K., Romania, and Poland. Participants were randomly assigned to receive two divided doses of 1,000 mg of CBD daily or two doses of the placebo to be taken alongside their regularly prescribed antipsychotic medication regime.

Following the 8-week trial, the researchers found significant changes in the CBD group when compared to the placebo group. Positive psychotic symptoms were significantly reduced from baseline to the end of the study for the CBD group. Most notably, before unblinding, patients from the CBD group were rated as “improved” by their treating clinicians significantly more than those from the placebo group. Adverse effects were mild and reportedly resolved on their own. Other differences existed between the groups, such as improved Global Assessment of Functioning scale (GAF) scores, cognitive ability, and motor skills, although these results were not statistically significant.

“The trend for an overall improvement in cognitive performance raises the possibility that CBD may have beneficial effects on cognition,” the authors write. “Post hoc analyses indicated that the strongest improvements were in motor speed and executive functioning.”

This study provides support for more research examining the role CBD may play in treating psychotic symptomology. The authors conclude, “Because CBD acts in a way different from conventional antipsychotic medication, it may represent a new class of treatment for schizophrenia. However, its potential clinical utility will require further investigation in larger-scale trials.”



McGuire, P., Robson, P., Cubala, W. J., Vasile, D., Morrison, P. D., Barron, R., … & Wright, S. (2017). Cannabidiol (CBD) as an adjunctive therapy in schizophrenia: a multicenter randomized controlled trial. American Journal of Psychiatry175(3), 225-231. (Link)


  1. This reminds me of an item in the old compilation Orthomolecular Psychiatry edited by Linus Pauling and David Hawkins in1974. In an essay by Hawkins describing the North Nassau Mental Health Center, which he ran, he mentioned that the doper patients he had (in the glory days of psychedelic abuse) who only smoked marijuana didn’t relapse like the poly-dopers who were also his patients and were getting basically the same treatments as the others. Perhaps this is related to some of the stuff in this article about CBD.

  2. “Agents with anticholinergic properties (e.g., sedating antihistamines; antispasmodics; neuroleptics; phenothiazines; skeletal muscle relaxants; tricyclic antidepressants; disopyramide) may have additive effects when used in combination … Central symptoms may include memory loss, disorientation, incoherence, hallucinations, psychosis, delirium, hyperactivity, twitching or jerking movements, stereotypy, and seizures.” From

    How different are the central symptoms of anticholinergic intoxication syndrome from the positive symptoms of schizophrenia? Not very. But since antipsychotic induced anticholinergic toxidrome is not listed in the DSM billing code “bible,” it is always misdiagnosed as one of the billable, but “invalid,” DSM disorders.

    Perhaps, weaning people off a drug class (neuroleptics/antipsychotics) that actually creates the positive symptoms of “schizophrenia” would be more effective than giving them more drugs? The neuroleptics create the negative symptoms of “schizophrenia,” too.

    Given the reality that the “schizophrenia” treatments create all the symptoms of “schizophrenia,” it’s highly likely that the primary etiology of “schizophrenia” is the “schizophrenia” treatments themselves.

  3. speaking of Orthomolecular, I got to thinking the other day…what if, over the long haul (years of “treatment,” which often involves both Rx and the vitamins), a big part of what makes Orthomolecular so effective in bringing about “recovery” is simply reducing psych drug toxicity and improving overall health? That, and…the Orthomolecular doctors were (and are, based on the more modern material I’ve skimmed over) acutely aware of the reality of the “tranquilizer psychosis,” and it seems they do their best to select drugs and dose drugs accordingly.

    I mention this because I kind of wonder if part of what’s going on here is that adminstering a calming, relaxing, soothing, perhaps even pleasant to take (I hope so, anyway) substance might also help reduce psych drug toxicity, too. Kind of how benzodiazepines were (and are, at times) used long term in “Schizophrenic” people, and the combination sometimes helps keep the neuroleptic dose lower and “augments treatment,” basically by calming frayed nerves and probably also by helping with neuroleptic induced dysphoria and akathisia, as well. Older data showed that some people with “Schizophrenia” did a-OK taking sufficient quantities of Valium during the “prodromal phase,” which I’m thinking means they took a reasonably pleasant sedative only when things got rough, and their overall results were good.

    at a practical level, it seems that new “treatments for Schizophrenia” will, in fact, be used to “augment standard treatment,” because the neuroleptic=”antipsychotic”=”life saving, necessary, lifelong treatment” dogma is basically part of The Psychiatric Catechism. it is what it is, I suppose. I’m beginning to think that the best many of us who are now so thoroughly disillusioned and disgusted can do is get out, warn those whom we can, and hope that the the next generation of “patients” at least get less toxic drugs and other “treatments.”

    • I also wonder if OrthoPsych contributes to increasing hope and a sense of agency in the recipient, beyond whatever concrete physiological health issues are being addressed. One of the worst things about the psychiatric model is that it tells people there is nothing they can do about their “broken brains.” It seems that OMP challenges that directly and says, “Yes, you can!”