The experience of stress can have a damaging impact on physical and mental health. Cortisol is a biomarker of psychological stress and a key product of the biological stress response. Support from a romantic partner has been shown to reduce biological stress reactivity through suppression of salivary cortisol levels in response to a stressor, buffering the negative impact of stress on health (Kirschbaum et al., 1995; Ditzen et al., 2008). Ethnic disparities in health exist, with increased rates of disease and poorer health outcomes for minority groups. Despite this, little is known about the influence that ethnicity may have on the physiological response to acute stressors or the effectiveness of partner support in response to a stressor. The aim of the current study was to identify whether ethnicity influences cortisol secretion in response to the Trier Social Stress Test (TSST), an acute laboratory stress task both with and without partner support, in two countries (USA, UK). 61 participants from the United States and 24 participants from the United Kingdom completed the TSST. Ethnicities varied with 49% White, 27% Black, 9% Hispanic, 7% Asian, and 7% of participants stating ‘other’. The TSST was administered either with or without the element of partner support before the stressor, and salivary cortisol samples were collected at baseline, post-task, and 10, 25, and 40 minutes post-task. Results indicated that nationality and ethnicity yielded a significant main effect for cortisol secretion with US Blacks showing blunted cortisol secretion across the TSST. Interaction effects for both variables were approaching significance when analysed with condition, with Black and US participants showing the most reduction in cortisol secretion when supported by a partner. These findings are novel, indicating a significant difference in cortisol secretion among ethnicities, and across two nationalities, indicating that both ethnicity and nationality are significant predictors of cortisol reactivity to an acute stressor. The findings of this study may provide evidence for a biological mechanism for the ethnic disparities seen in negative health outcomes.
