Who still suffers? Effects of COVID-19 stressful experiences on somatic symptoms and anxious mood moderated by diurnal cortisol: A daily diary study

This daily diary study drew on the allostatic load model to examine the predictive effect of COVID-19 stressful experiences (CSE) on somatic symptoms and anxious mood, as well as applying the biological sensitivity to context model to explore whether diurnal cortisol moderated the above associations. A total of 101 Chinese college students retrospectively reported CSE in October 2020, followed by 5-day diary reports on somatic symptoms and anxious mood in November 2020, with salivary cortisol collected on Days 2 to 4 to measure cortisol awakening response (CAR), diurnal cortisol slope (DCS), and daily cortisol output (area under the curve with respect to ground, AUC_g). Results of multilevel models showed that greater CSE predicted more somatic symptoms but not anxious mood, which was only observed at flatter CAR, flatter DCS, or low AUC_g. Furthermore, three-way interactions of CSE, CAR, and AUC_g significantly predicted both somatic symptoms and anxious mood. Specifically, greater CSE predicted more somatic symptoms at flatter CAR with low AUC_g, while predicting higher anxious mood at flatter CAR with high AUC_g. Our findings demonstrate the long-term consequences following the prior pandemic, especially highlighting the biological vulnerability related to the synergetic effects of diurnal cortisol rhythms and daily cortisol output.