Protracted stress-induced hypocortisolemia may account for the clinical and immune manifestations of Long COVID.

About one out of eight people to convalesce from COVID-19 suffer from the so called Long COVID, a syndrome of non-specific symptoms with unclear pathogenesis. In a recent study published in Cell Long COVID participants reporting respiratory symptoms had low cortisol levels. In an as yet unpublished analysis from Yale University low plasma cortisol levels discriminated Long COVID from asymptomatic convalescent or healthy non-infected controls. Although various immune perturbations were present in Long COVID, low levels of cortisol were prominent and strikingly, depression and anxiety were increased. It has become clear that Long COVID features may be similar to those described in myalgic encephalomyelitis/chronic fatigue syndrome, post-SARS sickness syndrome, and various chronic stress syndromes which have been linked to hypocortisolemia. Notably, lack of response of the hypothalamic-pituitary-adrenal axis to hypocortisolemia shows a suppressed axis in Long COVID. We suggest that the inability of hypothalamic-pituitary-adrenal axis to recover after the acute illness, perhaps due to protracted stress in predisposed individuals, may represent the pathogenetic basis of the Long COVID-associated clinical and immunological manifestations.