Prevalence of DSM III schizophrenia among the first‐degree relatives of schizophrenic probands

The extent of the genetic component, if any, in DSM III schizophrenia still remains unresolved. To further examine the issue, the first-degree relatives of 116 DSM III schizophrenic probands in our department were compared with those of an equal number of normal subjects, randomly selected and matched for age and sex. More than three fourths of the surviving relatives of each group were interviewed and rated according to DSM III criteria. Information of varying degrees of completeness was obtained about the remainder (surviving and dead). The gathered data were sufficiently detailed to provide general evidence that schizophrenia, and schizophrenia-related personality disorders were significantly more common in the first-degree relatives of DSM III schizophrenic probands than in the relatives of the controls. These findings suggest that even narrowly defined schizophrenia, such as that obtained by using DSM III criteria, has also a genetic component.