Figure 1

Systemic infection produces a peripheral cytokine response, which in turn produces a cytokine response in the brain. Cytokines within the brain induce a well-characterized set of adaptive behaviors that are intended to help fight infection, including reduced appetite (food and water intake), increased sleep and decreased overall activity, reduced social interactions, and altered cognitive function. Many neuropsychiatric or mood disorders exhibit a similar set of behavioral symptoms that have become prolonged or exaggerated, including chronic metabolic disorders or decreased appetite, chronic sleep disturbances/fatigue, altered social interactions, withdrawal/depression, and decreased cognitive function (e.g. learning disabilities, dementia, and delirium). Not surprisingly, many neuropsychiatric disorders are also associated with altered immune/neuroimmune function.