Neuroinflammation is traditionally defined as the brain's innate immune response and is also considered to be a glial-cell propagated inflammation. Increasing evidence indicates that neuroinflammation plays an important role in some cases of major depression and also that antidepressants possess anti-neuroinflammatory properties. Inhibition of neuroinflammation may represent a novel mechanism of action of antidepressant treatment. In vivo studies with animal models of neurological conditions have shown that various types of antidepressants exert inhibitory effects on the expression of inflammatory mediators, including cytokines, as well as on both microgliosis and astrogliosis in the inflamed CNS. In vitro studies using pathologically activated rodent microglia or mixed glial cells have demonstrated that various types of antidepressants diminish glial generation of inflammatory molecules. One of the most plausible mechanisms of such anti-neuroinflammatory efficacy of the drugs, as well as their antidepressant actions, seems to involve elevated intracellular cAMP levels. But the exact mechanism has still to be elucidated.