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Objective The idea that distinct psychosocial factors may underlie specific patterns of neuroendocrine stress responses has been a topic of recurrent debate. We examined a recent contribution to this debate, the Social Self Preservation Theory, which predicts that stressors involving social evaluative threat (SET) characteristically activate the hypothalamic-pituitary-adrenal (HPA) axis. Methods Sixty-one healthy university students (31 females) performed a challenging speech task in one of three conditions that aimed to impose increasing levels of SET: performing the task alone (no social evaluation), with 1 evaluating observer, or with 4 evaluating observers. Indices of sympathetic (pre-ejection period) and parasympathetic (heart rate variability) cardiac drive were obtained by impedance- and electrocardiography. Salivary cortisol was used to index HPA activity. Questionnaires assessed affective responses. Results Affective responses (shame/embarrassment, anxiety, negative affect, and self-esteem), cortisol, heart rate, sympathetic, and parasympathetic activation all differentiated evaluative from non-evaluative task conditions (p<.001). The largest effect-sizes were observed for cardiac autonomic responses. Physiological reactivity increased in parallel with increasing audience size (p<.001). A rise in cortisol was predicted by sympathetic activation during the task (p<.001), but not by affective responses. Conclusion It would appear that SET determines the magnitude, rather than the pattern, of physiological activation. This potential to broadly perturb multiple physiological systems may help explain why social stress has been associated with a range of health outcomes. We propose a threshold-activation model as a physiological explanation for why engaging stressors, such as those involving social evaluation or uncontrollability, may appear to selectively induce cortisol release.

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African Americans have been consistently shown to have less deep (slow wave sleep; SWS) and more light (Stages 1 and 2) sleep than Caucasian Americans. This paper explored whether discrimination, a stressor that uniquely impacts certain ethnic groups, contributes to differences in sleep architecture. The sleep of 164 African and Caucasian Americans was examined with laboratory based polysomnography (PSG). Experiences of perceived discrimination (The Scale of Ethnic Experience) and sociodemographic factors were also assessed. After adjusting for age, body mass index (BMI), socioeconomic status (SES) and smoking status, African Americans slept approximately 4.5% more total sleep time (TST) in Stage 2 sleep and 4.7% less TST in SWS than Caucasian Americans (ps< .05). Perceived discrimination was a partial mediator of ethnic differences in sleep architecture. Individuals who reported experiencing more discrimination slept more time in Stage 2 and less time in SWS (ps< .05). Results suggest that the impact of stress related to ethnic group membership plays a part in explaining differences in sleep architecture.

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