Clinical similarities in siblings with schizophrenia

Three symptom groups, identified by factor analysis of schizophrenic symptoms, together with other clinical variables, were compared among 80 sibships (169 individuals) containing two or more members affected with schizophrenia. The three factors, which were labelled negative symptom disorganization, and reality distortion, all showed a moderate but significant degree of correlation between siblings. Age at onset was also significantly correlated. Such a familial pattern of clinical heterogeneity suggests underlying common familial aetiologies that influence the clinical form of the disorder. Whether these are genetic or environmental requires further investigation. This finding confers some external validation on the three factor model. It may be feasible to develop familial symptom patterns as the basis for an a priori approach to linkage heterogeneity.