What can experimental studies tell us about paranoia and anxiety? A systematic review with implications for theory and clinical practice

ABSTRACT Background Psychosis is one of the most disabling and costly long-term conditions, and treatment outcomes remain modest. Interventions focused on specific symptoms, such as paranoia, show promise and typically target cognitive and behavioural maintenance processes. Anxiety is implicated in theories of paranoia; however, the nature of the relationship remains unclear. We review experimental studies of paranoia and anxiety against existing cognitive models. Method A systematic review strategy identified experimental studies assessing levels of anxiety and paranoia. Papers were assessed for quality, and data relating to samples, measures, designs and key findings were extracted and narratively synthesised. Results Nineteen studies met criteria for the review. Most found that manipulations impacting anxiety also impacted paranoia, with preliminary evidence for a causal relationship. The overall quality of the research was weak. Discussion We recommend a research agenda to confirm initial evidence for the causal role of anxiety in increased paranoia, and whether targeting affect, in addition to cognitive and behavioural maintenance processes, improves outcomes in clinical groups and those at risk of psychosis.