Changes in psychological and cognitive variables as well as cortisol levels in recovered Covid-19 patients: a longitudinal study

Background: Decreased psychological and cognitive functioning is one of the complications of Covid-19 disease. We aimed to evaluate mental health, cognitive functioning, and salivary cortisol levels in Covid-19 patients with different disease severities in three 45-day intervals after recovery. Methods: 258 Covid-19 patients were assigned into three groups based on their disease severity: 112 patients in mild group, 67 patients in moderate group and 79 patients in severe group. The participants underwent psychological evaluations (including Depression, Anxiety and Stress Scale questionnaire, Beck Depression Inventory, SpeilBerger State-Trait Anxiety Inventory, Pittsburgh Sleep Quality Inventory), cognitive assessments (The Paced Auditory Serial Addition Test) and salivary cortisol level evaluation in three 45-day periods. Non-parametric statistical methods were applied for psychological and cognitive indicators, while two-way mixed model ANOVA was used to evaluate the cortisol concentration in three replications. Results: The group of mild patients became more anxious and the group of moderate patients became more anxious and depressed. But all three groups of patients developed severe sleep disorders over time. For cognitive functioning, although the results showed a decrease in the correct response rate, a significant increase in the correct response rate was observed in all three groups in all three measurements. However, the response speed not only did not increase, but also decreased in severe group. Cortisol level had a markedly increasing trend in all three groups. Conclusion: Improvement of cognitive functioning was in line with the increase in cortisol. Besides, the decrease in mental health had no effect on the cognitive functioning.