Is depression an inflammatory condition? A review of available evidence.

The current review examines the relationship between depression and the inflammatory immune response. Mood disorders are a significant cause of morbidity and the etiology of depression is still not clearly understood. Many studies have shown links between inflammatory cytokines and mood disorders, including elevated level of cytokines like tumour necrosis factor-alpha (TNF alpha), Interleukins (IL-1,IL-6) and others. Raised levels of cytokines have been shown to increase depressive behaviour in animal models, while many anti-depressants reverse this behaviour alongside reducing the Central Nervous System (CNS) inflammatory response and reduction in the amounts of inflammatory cytokines. Cytokines reduce neurogenesis, Brain Derived Neurotrophic Factor (BDNF) and neuronal plasticity in the CNS, while many anti-depressants have been shown to reverse these processes. The considerations of anti-depressants as anti-inflammatory agents, and implication of other anti-inflammatory therapeutics for the treatment of depression are pointed out.