Evidence-Based Reviews

Cannabidiol for psychosis: A review of 4 studies

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3. O’Neill A, Wilson R, Blest-Hopley G, et al. Normalization of mediotemporal and prefrontal activity, and mediotemporal-striatal connectivity, may underlie antipsychotic effects of cannabidiol in psychosis. Psychol Med. 2020;1-11. doi: 10.1017/S0033291719003519.

In addition to their key roles in the psychopathology of psychosis, the mediotemporal and prefrontal cortices are involved in learning and memory, and the striatum plays a role in encoding contextual information associated with memories. Because deficits in verbal learning and memory are one of the most commonly reported impairments in patients with psychosis, O’Neill et al6 used functional MRI (fMRI) to examine brain activity during a verbal learning task in patients with psychosis after taking CBD or placebo.

Study design

  • In a double-blind, randomized, placebo-controlled, crossover study, researchers investigated the effects of a single dose of CBD in 15 patients with psychosis who were treated with antipsychotics. Three hours after taking a 600-mg dose of CBD or placebo, these participants were scanned using fMRI while performing a verbal paired associate (VPA) learning task. Nineteen healthy controls underwent fMRI in identical conditions, but without any medication administration.
  • The fMRI measured brain activation using the blood oxygen level–dependent (BOLD) hemodynamic responses of the brain. The fMRI signals were studied in the mediotemporal, prefrontal, and striatal regions.
  • The VPA task presented word pairs visually, and the accuracy of responses were recorded online. The VPA task was comprised of 3 conditions: encoding, recall, and baseline.
  • Results during each phase of the VPA task were compared.


  • While completing the VPA task after taking placebo, compared with healthy controls, patients with psychosis demonstrated a different pattern of activity in the prefrontal and mediotemporal brain areas. Specifically, during verbal encoding, the placebo group showed altered activation in prefrontal regions. During verbal recall, the placebo group showed altered activation in prefrontal and mediotemporal regions, as well as increased mediotemporal-striatal functional connectivity.
  • After participants received CBD, activation in these brain areas became more like the activation seen in controls. CBD attenuated dysfunction in these regions such that activation was intermediate between the placebo condition and the control group. CBD also attenuated functional connectivity between the hippocampus and striatum, and lead to reduced symptoms in patients with psychosis (as measured by PANSS total score).


  • Altered activation in prefrontal and mediotemporal regions during verbal learning in patients with psychosis appeared to be partially normalized after a single 600-mg dose of CBD. Results also showed improvement in PANSS total score with CBD.
  • These findings suggest that a single dose of CBD may partially attenuate the dysfunctional prefrontal and mediotemporal activation that is believed to underlie the dopamine dysfunction that leads to psychotic symptoms. These effects, along with a reduction in psychotic symptoms, suggest that normalization of altered prefrontal and mediotemporal function and mediotemporal-striatal connectivity may underlie the antipsychotic effects of CBD in established psychosis.

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