The authors studied 49 alcoholic in patients in remission, 18 first-
degree relatives of 10 of these alcoholics, and 25 normal control subjects.
Alcoholic patients had significantly lower platelet monoamine oxidase (MAO)
activity than control subjects. There was an inverse relationship between
platelet MAO levels in the alcoholic patients and prevalence of reported
alcoholism in their first-degree relatives. First-degree relatives of
alcoholics had lower platelet MAO activity than control subjects. The data
suggest a relationship between low platelet MAO activity and predisposition
to familial alcoholism.