COVID-19 is associated with a high risk of complications from the central nervous system. Syndrome of cognitive disorders- in terms of memory, attention or executive functions among COVID-19 convalescents is often called brain fog (covid fog - CF). CF leads to psychomotor retardation and chronic fatigue syndrome, resulting in poor functioning and low quality of life. CF may affect up to 81% of patients after COVID-19. Prevalence of CF may be even greater among patients with severe forms of COVID-19. In the preliminary assessment authors found that 83% of COVID-19 inpatients had at least mild cognitive impairment. Moreover, SARS-CoV-2 infection is associated with higher incidence of depression and anxiety disorders. CF pathogenesis is not fully understood. There exist no strict diagnostic criteria for it, as well as no therapeutic recommendations. Health care systems of many countries, including Poland, lack therapeutic programs addressed at patients with CF. Tianeptine may be a drug with potentially beneficial effects in CF. Neuroprotective, antidepressive, sleep-improving and anxiolytic properties of tianeptine allow it to choose as a candidate for CF amelioration. There is also data supporting the thesis that patients with CF may benefit from short-term group therapy. It has been proven to improve quality of life, reduce stress, and improve cognitive function in non-MC cognitive disorders. Expected research results: A database will be created from the collected clinical, laboratory and additional data. Statistical models will be created to predict: the duration of disorders, response to therapy, the final result of treatment. Among the markers of CNS damage, those which correlates with the patient's condition will be selected. The study will allow to estimate the prevalence of CF in the population. PET-CT and auditory evoked potentials also will be used to expand knowledge in the field of CF. Based on the existing data, an improvement is expected in all investigated participants as a result of rehabilitation and psychotherapy. Additional improvement is expected in the tianeptine group. Improvement will be defined as: reduction in the severity of anxiety and depression disorders, reduction in the severity of cognitive disorders, improvement in the quality of life. The results will be used to develop a new diagnostic and therapeutic pathway and a comprehensive intervention program in CF.