Is Depression an Inflammatory Disorder?
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Studies consistently report that groups of individuals with major depressive disorder (MDD) demonstrate increased levels of a variety of peripheral inflammatory biomarkers when compared with groups of nondepressed individuals. These findings are often interpreted as meaning that MDD, even in medically healthy individuals, may be an inflammatory condition. In this article, we examine evidence for and against this idea by looking more closely into what the actual patterns of inflammatory findings indicate in terms of the relationship between MDD and the immune system. Data are presented in support of the idea that inflammation only contributes to depression in a subset of patients versus the possibility that the depressogenic effect of inflammatory activation is more widespread and varies depending on the degree of vulnerability any given individual evinces in interconnected physiologic systems known to be implicated in the etiology of MDD. Finally, the treatment implications of these various possibilities are discussed.
KeywordsMajor depression Fatigue Immune Inflammation Cytokines Interleukin-6 Tumor necrosis factor-α p38 mitogen-activated kinase Psychosocial stress Glucocorticoids Autonomic nervous system Tryptophan Kynurenine Quinolinic acid
Dr. Miller has received grant support and support for travel to meetings from the National Institute of Mental Health.
Dr. Raison has served as a consultant for Biolex Therapeutics and Pamlab.
Dr. Miller has served as a consultant for Schering-Plough Corp., GlaxoSmithKline, Abbott Laboratories, AstraZeneca, Roche, Pfizer, H. Lundbeck A/S, Wyeth, and Johnson & Johnson and has received grant support from Schering-Plough Corp., GlaxoSmithKline, and Centocor.
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