Genetic identification of a subgroup of depressed patients.

HLA antigens, blood groups and red cell enzyme polymorphisms were studied in patients with different types of affective disorders and in patients suffering from cycloid psychoses. Several statistically significant results were found. In particular, a subgroup of depressed patients characterized by a very extreme distribution of haptoglobin groups was identified. The implications of this last finding for the definition of a particular subgroup of depressed patients is discussed.