In recent years ideas about the influence of psychological status on physical health have been elevated from intuition and clinical lore to a legitimate area of scientific study. Mechanisms of influence are, indubitably, diverse. Some of this influence is indirect, accounted for simply by the instrumental help that social engagement, associated with good mental health, affords people; for example, psychologically "healthy" people are probably more likely to comply with medication regimens and engage in other healthful behaviors to a greater extent than those who are socially withdrawn or...