The fields of neuroscience, neuroimmunology, and psychiatry have seen remarkable growth over the past decade. For many years, it was believed that viruses, bacteria and other pathogens could precipitate psychiatric and neurological abnormalities. Recent developments in the field of neuroimmunology have provided insights into the possible relationships between immune function and behavioral disorders. Specifically, a physiological feedback loop between the brain and immune systems, notably involving cytokines, have been identified, thus permitting an analysis of how pathogens may come to potently alter brain function. Such changes may affect adaptive and abnormal behaviors. This book examines the nature of these relationships. Key topics include: basic mechanisms of neural-immune interactions; the effects of immunity on normal brain neurochemistry and behavioral processes; and how immune activity may contribute to clinical disorders such as schizophrenia, depression, aggression, pain and stress.