Post-COVID major depression is not associated with peripheral inflammation

Although post-COVID major depressive disorder (MDD) is frequent, the physiological mechanisms associated with it remain unclear. This study aimed to assess the association between 10 residual blood markers of inflammation and the presence of MDD 4 months after the acute phase of COVID-19.

This is a cross-sectional study of the COMEBAC cohort that followed patients 4 months after hospitalization for COVID-19 at Bicêtre Hospital. Patients with lingering symptoms or who had been in critical care (n = 177) were invited to a day hospital for assessment of MDD and peripheral inflammation. Ten peripheral inflammatory markers were examined: plasmatic C-reactive protein; leukocyte, monocyte, neutrophil, and lymphocyte counts; the neutrophil to lymphocyte ratio; the systemic inflammatory index (i.e., the (platelet x neutrophil) to lymphocyte ratio); cortisol, ferritin, and hemoglobin levels. Current MDD was assessed through structured interviews with a psychiatrist, depressive symptoms through self-questionnaires. Peripheral inflammatory markers were compared between patients with post-COVID MDD and patients without a lifetime history of psychiatric disorders (controls).

Out of 177 patients, 24 (13.6%) had MDD. No significant differences in peripheral inflammatory markers were observed between patients with post-COVID MDD and controls. Furthermore, peripheral inflammatory markers were not correlated with symptoms of depression.

We found no association between post-COVID MDD and 10 peripheral inflammatory markers 4 months after COVID-19 infection. Other potential mechanisms warrant investigation.