The genetics of schizophrenia: a reassessment using modern criteria.

The authors present two reasons for reassessing familial transmission of schizophrenia: recent major changes in diagnostic criteria and methodological weaknesses of older studies. Their own study of this subject employed narrowly defined, operational research criteria; prospective proband selection; semistructured family interviews; and blind, independent diagnoses of probands and relatives. For 30 schizophrenic probands they found an age-corrected morbidity risk in first-degree relatives of 1.61%, a figure that would only support familial transmission if the true population prevalence of schizophrenia were .2% or less. The authors conclude that the case for familial transmission of narrowly defined schizophrenia is weak and suggest alternative hypotheses.