Possible linkage between alpha-haptoglobin (Hp) and depression spectrum disease.

Depression spectrum disease is an unipolar depressive illness in which at least one member of the family has unipolar depression and at least one other first degree relative has alcoholism and/or antisocial personality; using this definition, 14 depression spectrum disease families are studied. Assuming, among other things, that variability in age of onset is environmentally caused and lognormally distributed, segregation analysis shows that the data are compatible with the dichotomy of 'affected' versus 'not affected' being due to an autosomal dominant gene. A simple environmental hypothesis in which the transmission of the illness does not depend upon the parents' type could be rejected (p less than 0.001). Linkage analysis is performed by the method of maximum likelihood, taking the best fitting Mendelian model found in the segregation analysis. The results show virtually no evidence of linkage between depression spectrum disease and C3, but suggestive evidence (lod score = 1.03) of linkage between depression spectrum disease and alpha-haptoglobin (both these linkages were previously suggested by significant results in sib-pair analyses).