Dominantly inherited diabetes, schizophrenia, or alcoholism in families of college graduates.

Abstract

Evaluation of family data on frequent human disorders, including diabetes mellitus, schizophrenia, and alcoholic tendency, leads to the conclusion that the most plausible genetic mechanism is dominant inheritance with incomplete penetrance. The high levels of the genes are presumed to reflect balanced polymorphic states connected with heterosis, and this conception has prompted a survey of the graduates of the Reykjavik College in Iceland to determine their lifetime risks of the three conditions. The scholars and their first-degree relatives show an increase in psychosis, which also is documented to exist at an even higher level in a subsam-ple of honor graduates. Some elevation of alcoholic tendency appears to be present in the older members, but not in those born more recently. No increase in diabetes can be detected.