The brain, depression, and the immune system

The brain influences and controls the immunologic mechanisms involved in the maintenance of health and bodily integrity. The influence on immune functioning is more likely lateralized with left cerebral involvement than right-sided involvement. Depression, along with the accompanying neuroimmune changes, is found more frequently after left cerebral lesions than after right-sided lesions. Stress, particularly uncontrollable stress, produces hypothalamic-pituitary-adrenal axis (HPA) dysfunction as measured by elevations in plasma adrenocorticotrophic hormone. These changes parallel those seen in many depressed patients. But caution is called for in assessing stress and depression. In everyday life, as opposed to the laboratory, the controllable versus uncontrollable paradigm is not as useful. Attitudes, spiritual resources, hopes, and ideals can neutralize the effects of an uncontrollable stress situation, such as prisoners of war and victims of religious or ethnic persecution might experience. Whether subjective differences in tolerance for such uncontrollable stresses are accompanied by distinguishing indicators of neuroimmune dysfunction has yet to be demonstrated.