The well-known huge global burden of unipolar depression is, at least in part, due to the higher prevalence of medical co-morbidities in affected subjects. We purpose to evaluate, in what extent, the increased medical co-morbidity is due to the genetic factors shared, both, by unipolar depression and some of the chronic medical diseases.

We performed a longitudinal retrospective research on data records of 248 subjects admitted in our psychiatric clinic during 2001 – 2005. Two control samples were done. First control sample consisted in 44 bipolar patients and the second control sample was represented by 59 persistent delusional subjects admitted in our clinic during the same period.

The positive family history of chronic medical disease was more consistent in unipolar depressions comparatively with controls, regarding several medical chronic diseases. More exactly, high blood pressure, coronary heart disease and neoplastic diseases were most prevalent among the grade 1 relatives of unipolar depressions comparatively with that existing among the grade 1 relatives of controls. Just in the case of coronary heart disease, the difference has reached statistical significance (depressives - m = 0.443, S.D. = \0.652; bipolars + delusionals - m = 0.252, S.D. = 0.499; t = 2,665, p = 0.008).

The higher prevalence of some of medical diseases among unipolar depressives comparatively with other categories of psychiatric patients could be explained by genetic perspective. For example, according with our research, unipolar depression and coronary heart disease could be viewed as two distinct phenotypes of two genotypes that shares somewhat similar alterations.