Psychoneuroimmunology

AbstractMind-body literature, in the form of magazines and self-help books on stress and healing, is full of definitive claims for the existence of powerful influences of emotions and psychosocial stressors on the immune system, leading to onset or progression of cancers or infectious diseases. This literature often makes explicit reference to research in psychoneuroimmunology to support these claims. Psychoneuroimmunology is a multi-disciplinary field that has grown rapidly during the last three decades at the crossroads of immunology, behavioural neurosciences, neuroendocrinology, and psychology. It studies mechanisms and functional aspects of bidirectional relationships between the brain and the immune system. Although still controversial, there is evidence that psychological events including emotions can and do influence the outcome of infectious, autoimmune, and neoplastic diseases via modulation of cells of the immune system. A surprising finding has been that immune events occurring in the periphery also affect mood, behaviour, and metabolism by modulating brain functions, thereby providing a biologically important link between the immune system and brain. The original discovery that activation of the innate immune system in the periphery causes clinical signs of sickness that are processed in the brain is now being extended to the involvement of the immune system in depressive disorders. This new information has solidified the idea that neurotransmitters, neuropeptides, neural pathways, and immune-derived signals such as cytokines are the minimal essential elements that permit the immune system and brain to communicate with one another. These new data offer the unexpected conclusion that the immune system is likely to be involved in not only how emotions affect health but also how immune events regulate the development and expression of emotions.