Brain diseases and disorders such as Alzheimer disease, Parkinson disease, depression, schizophrenia, autism, and addiction lead to reduced quality of daily life through abnormal thoughts, perceptions, emotional states, and behavior. While the underlying mechanisms remain poorly understood, human and animal studies have supported a role of neuroinflammation in the etiology of these diseases. In the central nervous system, an increased inflammatory response is capable of activating microglial cells, leading to the release of pro-inflammatory cytokines including interleukin (IL)-1β, IL-6, and tumor necrosis factor-α. In turn, the pro-inflammatory cytokines aggravate and propagate neuroinflammation, degenerating healthy neurons and impairing brain functions. Therefore, activated microglia may play a key role in neuroinflammatory processes contributing to the pathogenesis of psychiatric disorders and neurodegeneration.