BEHAVIORAL AND PSYCHOLOGICAL EFFECTS OF IMMUNE ACTIVATION - IMPLICATIONS FOR DEPRESSION DUE TO A GENERAL MEDICAL CONDITION

Infectious and many non-infectious diseases are associated with immune activation and the production of cytokines in the periphery and in th e brain. Studies on experimental animals indicate that cytokines withi n the brain induce a depression-like behavioral syndrome, characterize d by anhedonia, diminished interest in the environment, reduced libido , anorexia, weight loss, hypersomnia, psychomotor retardation, fatigue , and diminished cognitive functioning. Similar symptoms accompany med ical conditions that involve immune activation in humans. Moreover, de pressed mood and other depressive symptoms are induced in humans follo wing cytokine administration. Brain cytokines also affect the neuroche mical systems that are implicated in the pathophysiology of depression . Based on these findings, it is suggested that immune activation is i nvolved in the etiology and symptomatology of 'depression due to a gen eral medical condition'.