Depression has a Strong Relationship to Alterations in the Immune, Endocrine and Neural System

Epidemiological findings indicate a connection between depressive symptoms and changes in status of the immune system in depressed patients. This raises the possibility of causative connections. Theories on mechanisms for interactions between immune and affective systems – directly and via endocrine system – are evolving. Such hypothesized causative connections are supported by several findings. First, in depressed patients changes in the status of the immune system in vivo and ex vivo are seen. Also, depressive symptoms are seen in patients with altered immune status (physiologically, pathologically or chemically induced). Knowledge in this field may have implications regarding psychiatric follow up of physically ill people suffering from diseases caused by an altered immune system (long lasting infections, autoimmune diseases, hypersensitivity disorders) as well as disorders for which treatment and prognoses depends on the immune system (infections, cancer). Similarly, medical treatment of depressed patients may be adjusted by more specific knowledge about the interaction between neuroimmunology and depression. Important findings and the present knowledge and theories are reviewed. Keywords: Depression, immunology, endocrinology, neurology, inflammation, brain, psychiatry