Modern research criteria and the genetics of schizophrenia.

The authors assessed the relevance of narrowly defined diagnostic criteria to genetic research in schizophrenia in the nuclear families of 84 chronic schizophrenic probands compared with families of 90 normal control probands. The morbidity risk for narrowly defined schizophrenia in first-degree relatives of patients with the narrow diagnosis was significantly higher than the control rate (3.8% versus 0.3%). The rate of chronic schizophrenia in the relatives of all schizophrenic patients was also significantly higher than the control rate (7.1% versus 0.6%), as was the rate of "spectrum" disorders (33.4% versus 11.3%). The data support the case for familial transmission of narrowly defined schizophrenia.