BackgroundStudies of schizophrenics with persecutory delusions have shown cognitive biases in subjects who are deluded. It has been suggested that their delusions defend against depression. This study challenges the assumption that delusional disorder (DD) patients are covertly depressed.MethodClinical and demographic data and responses to questionnaires designed to assess schizotypy, depression, dysfunctional attitudes, attributional and attention biases were collected from 29 patients satisfying DSM–III–R criteria for DD. These were compared with 20 matched normal controls and results from published studies of schizophrenics.ResultsDD subjects did not show abnormal levels of overt or covert depression or schizotypy. They showed high levels of dysfunctional attitudes (P < 0.0001), a distinctive attributional style (P = 0.01), and increased attention to threat-related stimuli (P = 0.01).ConclusionsDD is a distinct disorder predicated upon sensitivity to threat and biases of attention and attribution. These findings may have implications for the cognitive therapy of these disorders.