[The microglia hypothesis of psychiatric disorders]

The etiology of psychiatric disorders such as depression and schizophrenia remains unclear while, in many aspects, the neuropathology of these disorders has recently been reported to be closely associated with neuroinflammation. Despite the fact that microglia comprise only < 10% of the total brain cells, microglia respond rapidly to even minor pathological changes in the brain and may contribute directly to neuroinflammation by producing various pro-inflammatory cytokines and free radicals. We and other researchers have recently shown the inhibitory effects of some antidepressants as well as some typical/atypical antipsychotics on the release of inflammatory cytokines and free radicals from activated microglia, both of which have recently been discovered to cause the synaptic pathology, a decrease in neurogenesis, and white matter abnormalities found in the brains of patients with psychiatric disorders. The microglia hypothesis of psychiatric disorders may shed new light on a therapeutic strategy for these disorders.