Misunderstanding the intentions of others: An exploratory study of the cognitive etiology of persecutory delusions in very late-onset schizophrenia-like psychosis

Objective: The objective of this study was to explore the cognitive etiology of persecutory delusion formation and maintenance in very late-onset schizophrenia-like psychosis (SLP). Method: Probabilistic reasoning, causal attributional style, and mentalizing ability were examined in 29 patients with SLP, 30 with onset of depression after the age of 60 years and 30 healthy comparison subjects. Results: Patients with SLP made significantly more errors than the healthy comparison group in deception, but not false belief, mentalizing tasks. There were no significant performance differences between groups on the probabilistic reasoning task or the attributional style task. Conclusions: Mentalizing errors may contribute to the development and maintenance of persecutory delusions in SLP. These patients do not appear to show the wider range of cognitive biases described in deluded patients with schizophrenia with onset in younger adult life.