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Cannabidiol (CBD) as an Adjunctive Therapy in Schizophrenia: A Multicenter Randomized Controlled Trial.

Am J Psychiatry. 2018 Mar 1;175(3):225-231. doi: 10.1176/appi.ajp.2017.17030325. Epub 2017 Dec 15.

McGuire P¹, Robson P¹, Cubala WJ¹, Vasile D¹, Morrison PD¹, Barron R¹, Taylor A¹, Wright S¹.

Summary of the article:

The aim of the present study served to explore the safety and effectiveness of cannabidiol CBD as an adjunctive treatment in schizophrenia. In this randomized double-blind trial, 83 patients were randomized in a 1:1 ratio to receive CBD (1000mg/day) or placebo alongside their existing antipsychotic medication for 6 weeks. The researches examined the effects of CBD on positive and negative psychotic symptoms, cognitive performance, level of functioning, and the treating psychiatrist’s overall clinical impression. Participants were assessed before and after treatment using the Positive and Negative Syndrome Scale (PANSS), the Brief Assessment of Cognition in Schizophrenia (BACS), the Global Assessment of Functioning scale (GAF), and the improvement and severity scales of the Clinical Global Impressions Scale (CGI-I and CGI-S). The safety and tolerability of CBD were monitored through the assessment of adverse events, clinical laboratory tests, and vital signs.

Results:

• Compared with the placebo group, the CBD group had lower levels of positive psychotic symptoms (PANSS: treatment difference = -1.4, 95% CI= -2.5,-0.2)
• CBD group was more likely to have been rated as improved (CGI-I: treatment difference= -0.5, 95%CI=-0.8, -0.1) and as not severely unwell (CGI-S: treatment difference = -0.3, 95%CI=-0.5, 0.0) by the treating clinician.
• CBD group also showed greater improvements that fell short of statistical significance in cognitive performance (BACS: treatment difference=1.31, 95% CI=-0.10, 2.72) and in overall functioning (GAF: treatment difference=3.0, 95% CI=-0.4, 6.4)
• CBD was well tolerated, and the rate of adverse events were similar between the CBD and the placebo group.
• Findings suggest that CBD has beneficial effects in patients with schizophrenia. CBD acts in a way different from conventional antipsychotic medication, such as inhibition of fatty acid amide hydrolase, inhibition of adenosine reuptake, TRPV1 and 5HT1A receptor agonism. This may represent a new class of treatment for schizophrenia. This will require further research in larger-scale trials.

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