Social contacts as modifiers of diurnal cortisol production : a potential pathway between social relationships and health

Social connections have been linked with morbidity and mortality across decades of research. Although stress buffering and health behavior models have been extensively detailed as pathways for this effect, the direct effects of social contacts on physiology have received less attention. Social contacts may help to regulate biological rhythms, particularly within the hypothalamic-pituitary-adrenal (HPA) axis, a hormonal system known to be influenced by the social environment. Dysregulation of the HPA axis has been associated with psychiatric illnesses such as depression. The current thesis includes three studies that investigated the relationship between social contact and the diurnal pattern of cortisol secretion, as well as the moderating role of depression. These relationships were examined both cross-sectionally and prospectively via daily diary assessment of daily social contacts and salivary cortisol levels. In the first study, depressed women had a blunted cortisol response to waking compared to non-depressed women. Among the non-depressed but not among depressed women, the number of social contacts (especially positive ones) was associated with cortisol response to waking. In the second study, data were analyzed using hierarchical linear modeling and within-person results revealed that cortisol slopes following a day with more social contacts were steeper compared to cortisol slopes following a day with fewer social contacts. In the third study, daily social contacts were manipulated using a within-subjects design. Participants experienced both high and low social contact conditions in the laboratory while continuing to collect ambulatory data on their daily social contacts and cortisol levels. Results show that the manipulation successfully altered daily social contacts, but had no significant effect on cortisol slope. However, there is some evidence to suggest that frequency of contact may be an important moderator of the effect. Although causality has not been definitively demonstrated, findings from these studies suggest that in addition to previously articulated pathways, social relationships may influence health via a direct effect of social contact on physiology.Arts, Faculty ofPsychology, Department ofGraduat