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

Abstract

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 been unclear. To ascertain the factor structure and familiality of nuclear symptoms. 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. Principal components analysis demonstrated two major factors: one, accounting for about 50% of the variance, groups thought withdrawal, insertion and broadcasting, with delusions of control; and the second, accounting for < 20% of the variance, groups together third-person voices, thought echo and running commentary. Factor I was significantly correlated within sibling pairs. The correlation within sibling pairs suggests that, contrary to the conclusion of some previous studies, some nuclear symptoms do show a degree of familiality and therefore perhaps heritability.