DEPRESSION, ADRENAL-STEROIDS, AND THE IMMUNE-SYSTEM

During the past decade, over 30 studies have examined the immune syste m in depression. While a number of investigators have reported depress ion-related alterations in peripheral blood immune cell number and fun ction, many researchers have been unable to replicate these findings. The relationship between depression and the immune system has turned o ut to be much more complex than was initially anticipated. Factors whi ch have complicated the interpretation of the research include the het erogeneity of depressed patients, the variability of immune assays, an d the clinical relevance of these assays. In this review we conclude t hat alterations in the immune system do not appear to be a specific or reproducible biological correlate of depression but may occur in asso ciation with other variables which characterize depressed patients inc luding age, sex and severity of depression. Conceptual frameworks for future research on the immune system and depression are discussed and include: (i) depression as a cofactor in the development, course and o utcome of diseases involving the immune system; (ii) depression as a n euroimmunological disease; and (iii) depression as a model for studyin g neuroendocrine-immune interactions in humans. In terms of this third line of research, patients with depression consistently have been sho wn to display abnormalities in the secretion of adrenal steroids, and new data is presented which indicates that adrenal steroids may play a much more complex role in the modulation of the immune response than has been previously appreciated.