Prior Expectations of Volatility Following Psychotherapy for Delusions: A Randomized Clinical Trial

Persecutory delusions are common, distressing, and difficult to treat. Testing computational neuroscience models of delusions can identify new therapeutic targets.

To determine whether change in delusion severity is associated with a corresponding change in volatility priors and brain activation estimated during a belief updating task.

This randomized clinical trial was conducted from April 9, 2021, to December 5, 2023, within the Vanderbilt University Medical Center Psychiatric Hospital and at a community mental health center in Nashville, Tennessee. Participants were adults (aged between 18 and 65 years) with schizophrenia spectrum or delusional disorder and an active, persistent (≥3 months) persecutory delusion with strong conviction (>50%). Participants were randomly assigned 1:1 to either cognitive behavioral therapy for psychosis (CBTp)-based intervention or befriending therapy. Intention-to-treat analysis was performed from June 1 to October 31, 2024.

The CBTp was a manualized intervention targeting persecutory delusions. The befriending therapy involved engaging in conversations and activities focused on neutral topics. Both interventions were provided in person, lasted for 8 weeks, and included standard care. Standard care consisted of medication management and ancillary services.

Primary outcomes were volatility priors (ie, prior expectations of volatility) derived from a 3-option probabilistic reversal learning task; persecutory delusion severity measured by the Psychotic Symptom Rating Scales (PSYRATS delusion subscale; score range: 0-16, with the highest score indicating severe preoccupation, distress, conviction, and functioning impact); and brain activation in the striatum and prefrontal cortex measured by blood oxygenation level-dependent signal change. Associations between volatility priors, clinical improvement, and change in neural activation were examined.

Sixty-two participants (median [range] age, 31 [19-63] years; 38 males [61%]) were randomly assigned to the CBTp (n = 32) or befriending therapy (n = 30) arms. A subgroup of 35 participants (57%) completed functional magnetic resonance imaging. Volatility priors decreased following treatment (F1,112 = 7.7 [P = .006]; Cohen d = 0.52 [95% CI, 0.15-0.90]), as did delusion severity (F1,112 = 59.7 [P < .001]; Cohen d = 1.50 [95% CI, 1.00-1.90]), across both groups. The decrease in volatility priors was not associated with clinical improvement in PSYRATS scores (F1,102.8 = 1.8 [P = .18]; Cohen d = 0.26 [95% CI, -0.12 to 0.65]). Activation in the caudate and prefrontal cortex significantly decreased following treatment. Decreased caudate activation was associated with decreased volatility priors (F1,58.3 = 16.6 [P < .001]; Cohen d = 1.07 [95% CI, 0.51-1.61]) but not with PSYRATS total scores. Associations remained significant after controlling for antipsychotic medication (F1,53 = 13.77; P < .001).

This randomized clinical trial found that elevated volatility priors and associated activation in the caudate nucleus were amenable to change. Volatility priors could be a potential target for intervention in psychosis.

ClinicalTrials.gov Identifier: NCT04748679.