Monocyte profiles and their association with depression severity and functional disability

Inflammatory processes have been implicated in the pathophysiology of depression. This study explores the association between the number, proportion and subtypes of monocytes with functional disability and depression severity in a sample of adult patients.

A cross-sectional study was conducted with 74 participants. The total number and proportion of monocytes were obtained from hemogram analysis and the subtypes (classical, intermediate, and non-classical) were quantified using flow cytometry. Depression severity was assessed using the 17-item Hamilton Depression Rating Scale (HDRS-17), and functional disability was measured via the Sheehan Disability Scale (SDS). Linear regression models adjusted for demographic and clinical covariates were applied to evaluate associations.

Total blood monocyte counts and their percentages were negatively correlated with functional disability scores (r = -0.27 and r = -0.26, respectively; p < 0.05). In contrast, elevated levels of intermediate and non-classical proinflammatory monocytes were positively correlated with depression severity (r = 0.25, p < 0.05). Linear regression analysis revealed that a 1% increase in proinflammatory monocytes was associated with a 0.19-point increase in HDRS-17 scores (p = 0.009). Additionally, higher total and percentage monocyte counts were associated with reductions in functional disability scores by 10.63 units (p = 0.02) and 0.80 units (p = 0.04), respectively.

Monocytes play a dual role, contributing to both the initiation and resolution of inflammation. In this study, we found that monocytes may be involved in protecting functional responses while also reflecting depression severity. These findings underscore the potential of monocyte profiles as biomarkers for depression severity and functional impairment, highlighting the need for further research to elucidate the underlying mechanisms.