On two kinds of delusion of reference.

Although delusions of reference are one of the most common psychotic symptoms, they have been the focus of little research. The aims of the present research were, first, to determine whether it is possible to identify different kinds of referential delusions reliably and, if so, to investigate associations among them and between these delusions and other positive psychotic symptoms. Participants with a diagnosis of schizophrenia (n=57) were recruited from a volunteer register (n=26) and from inpatient psychiatric wards (n=31). They were interviewed with the Scale for the Assessment of Positive Symptoms (SAPS) except that the questions about ideas and delusions of reference were replaced with questions targeted at seven particular delusions and three content areas. Ratings were made independently by two assessors. Agreement between the assessors was high for all of the delusions of reference and other psychotic symptoms. A factor analysis of these ratings revealed two factors that represent delusions of communication and delusions of observation. Only delusions of observation were associated with hallucinations and persecutory ideation. Delusions of communication showed few significant correlations with other symptoms and therefore appear to require different explanations.