Factor structure and familiality of first-rank symptoms in sibling pairs with schizophrenia and schizoaffective disorder

Background Since their introduction as diagnostic criteria by Schneider in 1937, nuclear symptoms have played a key role in concepts of schizophrenia, but their relationship to each other and to genetic predisposition has bee n unclear. Aims To ascertain the factor structure and familiarity of nuclear symptoms. Methods Nuclear (Schneiderian) symptoms were extracted from case notes and interviews in a study of 103 sibling pairs with DSM-III-R schizophrenia or schizoaffective disorder. Results Principal components analysis demonstrated two major factors: one, accounting for about 50% of the variance, groups thought withdrawal, insert ion and broadcasting, with delusions of control; and the second, accounting for <20% of the variance, groups together third-person voices, thought ech o and running commentary. Factor I was significantly correlated within sibl ing pairs. Conclusions The correlation within sibling pairs suggests that. contrary to the conclusion of some previous studies, some nuclear symptoms do show a d egree of familiality and therefore perhaps heritability.