One hundred depressive probands have been examined. A family history was obtained on each of the probands, and a family study was done on 129 primary relatives of these probands. An analysis of the genetic data is in favor of the possibility that at least two types of depressive illness exist. One of these may be called "depression spectrum disease." The prototype of this would be a female with an onset prior to age 40 in whose family more depression is seen in female relatives than male relatives and the deficit in males is made up by alcoholism and sociopathy. The second prototype is that of pure depressive disease in which the proband is a male whose illness starts after age 40 and in whom there are equal amounts of depression in both male and female relatives and no large amount of alcoholism or sociopathy in the males.
Winokur G, Cadoret R, Dorzab J, Baker M. Depressive DiseaseA Genetic Study. Arch Gen Psychiatry. 1971;24(2):135-144. doi:10.1001/archpsyc.1971.01750080039006