The post-COVID stress syndrome: from the three-stage stress response of Hans Selye to COVID-19.

Stress is the nonspecific response of the body to any demand made upon it, as defined by Hans Selye more than 80 years ago, based on his animal experiments at McGill University in Montreal, Canada. By emphasizing 'nonspecificity' he tried to underline that stress response is elicited my several factors, like nowadays in COVID-19, e.g., fear of infection, social isolation, death in family, loss of employment, etc. Thus, COVID-19 has been the largest new human stressor in the twenty-first century. Selye's studies in rats also revealed 3 stages of stress response: the short initial "alarm reaction" is followed by a longer "stage of resistance", associated with increased levels of corticosterone that is often terminated by a "stage of exhaustion", referring to an exhausted adrenal cortex when the secretion of glucocorticoids drops. Fast forward, that is exactly what has been documented in severe cases of infections caused by the SARS-CoV-2 virus: in hospitalized COVID-19 patients initially the blood levels of cortisol not only have been elevated, but only those with high concentration of this natural anti-inflammatory corticosteroid survived vs. those who had low levels of cortisol, suggesting diminished adrenocortical functions. Furthermore, patients with very severe cases of COVID-19 who ended up in intensive care units had significantly low cortisol blood levels, compared to patients with equal severity of diseases due to other causes. Thus, these 'natural phenomena' in clinical medicine, unfortunately confirmed Selye's studies in experimental animals several decades ago. Still, the good news is that astute clinicians empirically recognized this and started to give potent synthetic glucocorticoids such as dexamethasone to severe COVD-19 patients and this beneficial effect of exogenous corticoids has been extensively confirmed in the scientific literature.