Preliminary evidence suggests that cannabidiol (CBD) may be effective in the treatment of neurodegenerative disorders; however, CBD has never been evaluated for the treatment of cognitive impairments associated with schizophrenia (CIAS).
This study compared the cognitive, symptomatic, and side effects of CBD versus placebo in a clinical trial.
This study was a 6-week, randomized, placebo-controlled, parallel group, fixed-dose study of oral CBD (600 mg/day) or placebo augmentation in 36 stable antipsychotic-treated patients diagnosed with chronic schizophrenia. All subjects completed the MATRICS Consensus Cognitive Battery (MCCB) at baseline and at end of 6 weeks of treatment. Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS) at baseline and biweekly.
There was no main effect of time or drug on MCCB Composite score, but a significant drug × time effect was observed (p = 0.02). Post hoc analyses revealed that only placebo-treated subjects improved over time (p = 0.03). There was a significant decrease in PANSS Total scores over time (p < 0. 0001) but there was no significant drug × time interaction (p = 0.18). Side effects were similar between CBD and placebo, with the one exception being sedation, which was more prevalent in the CBD group.
At the dose studied, CBD augmentation was not associated with an improvement in MCCB or PANSS scores in stable antipsychotic-treated outpatients with schizophrenia. Overall, CBD was well tolerated with no worsening of mood, suicidality, or movement side effects.
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Conflict of interest
Support granted by the Stanely Medical Research Institute.
Mohini Ranganathan has in the past 3 years or currently received research grant support administered through Yale University School of Medicine from Insys Therapeutics and Pfizer Inc. Deepak Cyril D’Souza has in the past 3 years or currently received research grant support administered through Yale University School of Medicine from Pfizer Inc. Pfizer, Inc. had a role in the design and conduct of the study: collection, management, analysis, and interpretation of the data; preparation, review, and approval of the manuscript; and the decision to submit the manuscript for publication. Andrew Davies is a founder and full time employee of STI Pharmaceuticals Ltd (UK). Douglas Boggs, Aarti Gupta, John Cahill, Brian Pittman, Ashley Schnakenberg Martin, Halle Thurnauer, Swapnil Gupta, and Toral Surti report no financial relationships with commercial interests.
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Boggs, D.L., Surti, T., Gupta, A. et al. The effects of cannabidiol (CBD) on cognition and symptoms in outpatients with chronic schizophrenia a randomized placebo controlled trial. Psychopharmacology 235, 1923–1932 (2018). https://doi.org/10.1007/s00213-018-4885-9