Involvement of the HPA axis in bond formation provides a mechanism through which social and environmental cues can influence social structure. Once a stable social bond has been established, positive social interactions may result in a buffering against some types of stressors. This observation forms the basis of a wide range of social-bonding phenomena including the positive effects of pet visitation to nursing homes (Counsell, Abram, and Gilbert, 1997), the importance of friendships and social networks for surviving cardiovascular disease and accidents (Kawachi, Colditz, Ascherio, Rimm, Giovannucci, Stampfer, and Willett, 1996), and the positive effects of marriage on longevity (Tucker, Friedman, Wingard, and Schwartz, 1996). The mechanism through which social bonds improve health and well-being is not known but may involve OT-induced suppression of the HPA axis.