Possible linkage between group-specific component (Gc protein) and pure depressive disease.

Genetic linkage was studied in pure depressive disease, a subgroup of unipolar depression defined by absence of familial alcoholism and/or antisocial personality. Rigorous research criteria were used for diagnosis and the diagnoses were made blind, i.e. without the knowledge of the genetic marker results. Under the assumptions of full penetrance and of all examined individuals' having passed the risk period, two out of eight families investigated showed a possibility of linkage, using the lod score method, with the Group-Specific Component (Gc protein) locus, one of the 17 polymorphic markers tested. The results, being based on a small amount of data, are presented as a hypothesis only; important possible implications of Psychiatry, however, indicate the desirability of testing the hypothesis.