The effects of momentary loneliness and COVID-19 stressors on hypothalamic–pituitary adrenal (HPA) axis functioning: A lockdown stage changes the association between loneliness and salivary cortisol

The COVID-19 pandemic can be characterized as a chronic stressor affecting the hypothalamic–pituitary–adrenal (HPA) axis, indexed by glucocorticoids (e.g., cortisol). We investigated whether salivary cortisol level is increased during a lockdown and whether a lockdown condition affects the association between loneliness, specific COVID-19 related stressors and salivary cortisol level. We conducted a smartphone-based ecological momentary assessment (EMA) study with 280 participants in Germany who experienced at least mild loneliness and distress amid COVID-19 from August 2020 to March 2021. We measured their momentary loneliness and COVID-related stressors including worries, information seeking behaviors and feelings of restriction during “no-lockdown” or “lockdown” stages amid COVID-19. Their salivary cortisol was measured 4 times on the last day of a 7-day EMA study. We found a significant increase in salivary cortisol levels during lockdown compared to no-lockdown. Lockdown stage was found to moderate the relationship between momentary loneliness and salivary cortisol level, i.e., loneliness was positively related to cortisol level specifically during lockdown. Mechanisms explaining the effect of forced social isolation on the association between loneliness and salivary cortisol need to be investigated in future studies.