Abstract

Oxytocin is a hormone and neuropeptide that is traditionally known for its role in parturition and lactation in women. In the last few decades, researchers have theorized that oxytocin is involved in the human stress response. This theory, known as tend-and-befriend, posits that oxytocin promotes social support seeking in humans during stressful situations by inhibiting the traditional fight-or-flight response, promoting attention to socio-emotional stimuli, and enhancing feelings of trust. This theoretical framework, however, has received little attention by way of supporting evidence in human experimental research. In this dissertation, four studies are presented that investigate the role of oxytocin in (1) regulating the cortisol response to stress, (2) enhancing the perception of emotion in human faces, and (3) promoting trust and social-support seeking in distressed people, particularly women. Across these studies, oxytocin is experimentally manipulated using a nasal spray to examine its effects in humans in a double blind, placebo-controlled fashion. In the first study, a 24IU dose of intranasal oxytocin was shown to inhibit cortisol rise during physical stress. In the second study, oxytocin enhanced the perception of emotion in human faces. In the third study, oxytocin selectively improved dispositional trust in distressed participants following a stress induction, but not in those whose mood was euthymic in response to stress. In the final study, oxytocin increased perceived support in women during negative memory recall in the company of an experimenter, and decreased perceived support while recalling such memories in social isolation. Taken together, the results of this thesis support the role of oxytocin in stress-regulation and social cognition in humans. These results also suggest that the effect of oxytocin on social bonding (i.e. trust) may be dependent on the experience of distress, and that oxytocin-motivated social support seeking may have positive and negative consequences in both sexes, particularly in women, depending on the availability of social contact. This oxytocin-induced facilitation of social support seeking might explain why humans, particularly women, are more susceptible to stress-related mental illnesses such as major depressive disorder in the face of social conflict or in the absence of supportive social relationships.