Familial associations of subsyndromes of psychosis in affected sibling pairs with schizophrenia and schizoaffective disorder

Attempts to describe the clinical heterogeneity of schizophrenia have consisted of categorical subtyping acid a dimensional approach using factor analysis. The latter has yielded three dimensions or subsyndromes: positive, negative and disorganisation. The aim of this study is to explore to what degree these subsyndromes are correlated within 114 sibling pairs (185 individuals) with DSM-III-R schizophrenia or schizo-affective disorder who were assessed for the lifetime presence or absence of the positive, negative, affective and disorganisation subsyndromes. Ratings were based on the core symptoms of each subsyndrome using a modified Krawieka scale. First rank symptoms were also included in the analysis. Coincidence was assessed by application of the binomial theorem to the frequency of occurrence of subsyndromes in this set of siblings. The disorganisation subsyndrome was shared above chance expectation (chi(2) = 9.15, P < 0.01 for all sibling pairs). The significant results for the disorganisation subsyndrome suggest that it may be a suitable phenotypic marker for genetic linkage studies. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.