It has been suggested that an exaggerated self-serving bias may underlie the formation of paranoia. One goal of the present study was to explore whether an abnormality of attributional style is confined to patients with persecutory delusions or extends to currently non-deluded patients. A second goal was to test whether paranoid patients show an external-personal rather than an external-situational attributional style for blame. An attributional styles questionnaire was administered to psychiatric patients diagnosed with schizophrenia (n = 35), depression (n = 18), and anxiety disorders (n = 34), as well as a healthy control group (n = 28). For each event (positive or negative outcome) participants were asked to write down what may have led to this event, and then to endorse the degree to which this event was caused by others/circumstances or themselves. Assessment of the Likert scale ratings demonstrated that while healthy subjects displayed a significant self-serving bias, currently paranoid and non-paranoid schizophrenia patients performed intermediately between healthy participants and depressed patients. Analysis of coded verbal statements indicated that irrespective of event type (positive, negative) patients with persecutory delusions had an even-handed attribution bias, whereas all other groups predominantly regarded themselves as causal. The latter finding indicates that acute paranoia may be associated with a decreased locus of internal control, which may promote the occurrence of certain paranoid beliefs (e.g., feelings of alien control and passivity experiences, respectively).
- Self-serving bias