Genetic independence of manic-depression and schizophrenia.

Increasingly sophisticated twin and adoption research has demonstrated major genetic contributions to the etiology of manic-depression and schizophrenia. But studies disagree concerning whether the two are genetically related illnesses. This lack of consensus could be due to individual, regional, and temporal differences in the criteria used to diagnose the two conditions. This study is the first to employ the new DSM-III criteria. Schizophrenia was no more common in the 1,098 first-degree relatives of 100 male and 100 female manic-depressives than it is in the population at-large. This would appear to strengthen the view that manic-depression and schizophrenia are genetically unrelated diseases.