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Cannabinoid Shows Positive Results in Treating Schizophrenia

Mid-stage study demonstrates antipsychotic effects

Positive top-line results have been reported from an exploratory phase 2a placebo-controlled clinical trial of cannabidiol (CBD, GW Pharmaceuticals) in patients with schizophrenia who had failed to respond adequately to first-line antipsychotic medications.

The multicenter, double-blind, placebo-controlled trial enrolled a total of 88 patients who were treated for six weeks. To enter the study, the participants had to have been treated for a minimum of four weeks with a first-line antipsychotic medication and have a Positive and Negative Syndrome Scale (PANSS) total score of greater than 60. As a phase 2a proof- of-concept study, there was no single primary endpoint but a series of exploratory endpoints.

The patients remained on their antipsychotic medications and were randomly assigned to receive CBD or placebo as adjunctive therapy.

Over a series of endpoints, CBD was consistently superior to placebo, with significant differences being observed in the PANSS positive subscale (P = 0.018), the Clinical Global Impression of Severity ( P = 0.04), and the Clinical Global Impression of Improvement (P = 0.02). The proportion of responders (i.e., those showing an improvement in the PANSS total score of greater than 20%) receiving CBD was higher than that of participants receiving placebo, with an odds ratio of 2.65. CBD was also superior to placebo (P = 0.07) in the area of cognition. The Scale for Assessment of Negative Symptoms showed a trend in favor of CBD; this trend reached statistical significance for patients taking CBD in conjunction with a leading first-line antipsychotic medication. Most of the other endpoints also favored CBD and approached statistical significance in many cases.

CBD was not associated with serious adverse events and had an overall safety profile similar to that of placebo. The most common adverse events were diarrhea, nausea, and headache. Two subjects withdrew from the study because of treatment-related adverse events: one receiving CBD and the other receiving placebo.

Previous studies have indicated that CBD may be useful either as monotherapy or in combination with first-line antipsychotic agents.

Source: GW Pharmaceuticals; September 15, 2015.

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