A review of recent CBD-schizophrenia trials found further evidence for CBD reducing positive symptoms, inconsistent effects on cognition, and good tolerability even at high doses.
Psychiatrists treating schizophrenia, psychosis researchers, and pharmaceutical companies developing CBD-based antipsychotics.
CBD: evidence for positive symptoms; not negative; cognition inconsistent
What the researchers found
Recent trials focused on sub-acute schizophrenia, clinical high-risk for psychosis (CHR-P), and frequent cannabis users. There is further evidence for CBD reducing positive symptoms but not negative symptoms. Cognitive effects were inconsistent, with one study reporting worsening. One study found CBD caused sedation, but others reported good tolerability at high doses. The authors emphasize that properly designed Phase III trials following regulatory guidelines are needed.
Why it matters
CBD antipsychotic potential has generated significant interest because current antipsychotics have severe side effects. This update provides the most current clinical trial landscape and identifies what is still missing.
The numbers in context
CBD: further evidence for positive symptom reduction; no benefit for negative symptoms; inconsistent cognitive effects; one study reported worsening cognition; sedation in one study; good tolerability at high doses otherwise.
How the study worked
Narrative review of clinical trials published or initiated within the last 18 months investigating CBD for schizophrenia and related conditions.
What this study cannot tell us
Narrative review (not systematic); limited number of trials to review; heterogeneous study designs; most trials small; the "further evidence" builds incrementally rather than providing definitive answers.
How to read the evidence
Moderate: review of recent controlled trials, but trials are few and small.
When this study was published
Published 2020.
The bigger picture
The specificity of CBD effects (positive symptoms yes, negative symptoms no, cognition unclear) is clinically important. It suggests CBD may work through a different mechanism than traditional antipsychotics, which is both its promise (novel target) and limitation (may not address the full syndrome).
Questions still open
- Will CBD be effective as monotherapy or only as an adjunct? Which combinations of CBD with existing antipsychotics are safe and effective?
Common questions
Can CBD treat schizophrenia?
Is CBD safe at high doses for psychosis?
Read the original research
Cannabidiol as a treatment option for schizophrenia: recent evidence and current studies.
Current opinion in psychiatry, 33(3), 185-191
Citation
Schoevers, Julie; Leweke, Judith E; Leweke, F Markus. (2020). Cannabidiol as a treatment option for schizophrenia: recent evidence and current studies.. Current opinion in psychiatry, 33(3), 185-191. https://doi.org/10.1097/YCO.0000000000000596
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