CBD augmentation showed no improvement in cognitive or psychotic symptoms compared to placebo in chronic schizophrenia.
Summary
n=36 stable antipsychotically treated patients with chronic schizophrenia; 6-week CBD 600 mg/d vs. placebo as augmentation. No main effect on MCCB total score; significant drug×time effect (p=0,02), but only the placebo group improved (p=0,03). PANSS total decreased over time (p<0,0001), no significant difference between groups (p=0,18). Negative RCT — CBD augmentation did not improve cognition or symptoms.
P
PopulationOutpatients with chronic schizophrenia under stable antipsychotic treatment, n=36
I
InterventionOral CBD 600 mg/day, 6 weeks, as augmentation to existing antipsychotic therapy
C
ControlPlacebo (oral, as augmentation)
O
OutcomeNo significant main effect of CBD on MCCB total score; significant drug×time interaction (p=0,02), with only the placebo group showing improvement over time (p=0,03); no significant drug×time effect on PANSS total score (p=0,18)
Confidence in the evidence
Very lowLowModerateHigh
Moderate
The third of four GRADE levels, the effect estimate is probably reliable.
<h4>Rationale</h4>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).<h4>Objective</h4>This study compared the cognitive, symptomatic, and side effects of CBD versus placebo in a clinical trial.<h4>Methods</h4>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.<h4>Results</h4>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.<h4>Conclusions</h4>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.<h4>Trial registration</h4>https://clinicaltrials.gov/ct2/show/NCT00588731.