Resemblance of psychotic symptoms and syndromes in affected sibling pairs from the Irish Study of High-Density Schizophrenia Families: evidence for possible etiologic heterogeneity

The clinical manifestations of the schizophrenic syndrome (both narrowly and broadly defined) are moderately influenced by familial factors. From a familial/genetic perspective, schizophrenia as currently defined may be etiologically heterogeneous.