Per the cognitive model of positive symptoms (Garety et al. 2001), a delusion may develop in the context of underlying biopsychosocial vulnerabilities (i.e., a genetic predisposition) and stressful life circumstances. This combination can lead to emotional changes, one of the most common being anxious arousal (which may predispose individuals to judge ambiguous experiences as harmful). In this context, individuals may begin to develop a cognitive or perceptual disturbance, view an experience as anomalous, and seek alternative explanations for an event. Another key feature is the individual begins to appraise the experience as external to themselves. This appraisal is influenced by several key factors, which include:
The type of reasoning and attributional biases that can occur are jumping to conclusions, blaming others rather than themselves for why an event occurred, failure to consider something as a coincidental occurrence, looking for evidence consistent with one’s own belief system, and deficits in theory of the mind. An example of a dysfunctional schema for an individual with a persecutory (or paranoid) delusion is where an individual views themselves as vulnerable/inferior, sees others as powerful/threatening, and looks at the future as hopeless or uncertain (Beck et al. 2009). In sum, these processes can lead to the formation of a delusion. The set of cognitive and affective processes that have contributed to the delusion’s development are theorized to play a role in perpetuating the delusion.
The cognitive model for positive symptoms is a framework cognitive behavioral therapy (CBT) for psychosis therapists may use when they are developing an individual’s formulation. In a 2018 meta-analysis that included 40 CBT studies, CBT was significantly efficacious for improving positive symptoms of schizophrenia in comparison to both treatment as usual and an inactive control (Bighelli et al. 2018), and has been shown to be efficacious for delusions, specifically (Mehl, Werner, and Lincoln 2015). Please refer to this free SMI Adviser webinar: Cognitive Behavioral Therapy for Psychosis: Understanding the Basics (February 2019).