Are theory of mind deficits in understanding intentions of others associated with persecutory delusions?

The purpose of this study was to investigate the association of the Theory of Mind ability to infer intentions of others and delusions in patients with schizophrenia-spectrum disorders. In a cross-sectional design, patients with acute persecutory delusions (PD) (n = 33), patients with remitted persecutory delusions (PD-rem) (n = 25), and non-clinical controls (n = 58) completed a movie task, in which they had to infer the characters' intentions and emotions and a false-belief task. Delusions were rated by observers and by the patients. Patients with PD were specifically impaired in the ability to infer intentions compared with patients with remitted delusions and controls. The ability to infer intentions predicted a significant amount of variance in delusions, even when executive functioning was controlled. Implications for models explaining the development and maintenance of delusions are discussed.