Effect of cannabidiol on schizophrenia based on randomized controlled trials: A meta-analysis

Studies and treatments of schizophrenia with cannabidiol (CBD) alone have been reported. However, there have been a variety of different results of the effects of CBD in schizophrenic patients based on the positive and negative syndrome scale (PANSS). Thus, the present meta-analysis aimed to determine the effects of CBD on schizophrenia. We searched internet databases and identified 774 potentially relevant studies, among which nine studies were ultimately included in our present meta-analysis. Our results showed that CBD treatments significantly decreased PANSS positive scores (95% CI, −2.51, −0.89, P = 0.27, I² = 18%) but had no effect on other PANSS scores. Interestingly, while the safety of CBD has continued to be further demonstrated over time despite the dosage of CBD being gradually increased, the dosage of delta-9-tetrahydrocannabinol (THC) has remained essentially unchanged. Following our present meta-analysis, we suggest possible mechanisms of CBD-based amelioration of schizophrenic symptoms, such as CBD-induced increases in fronto-striato-thalamic coupling.