Objective
This study aimed at investigating a set of peripheral cytokines in elderly female patients with MDD, comparing them to controls, and assessing the potential influence of clinical comorbidities on inflammatory markers.

Methods
Twenty-five elderly female patients diagnosed with MDD and 19 age-matched female controls were enrolled on this study. Plasma levels of interleukin (IL)-4, IL-6, IL-10, interferon (IFN)-γ and tumor necrosis factor (TNF)-α were evaluated with commercially-available assays.

Results
Elderly female patients with MDD exhibited higher plasma IL-6 and IL-4 levels when compared to controls. In a logistic regression model taking cytokine levels, comorbidities, and age into account, only type 2 diabetes mellitus (DM2) remained associated with MDD.

Conclusion
Diabetes influences the association between MDD and higher levels of cytokines in elderly female patients. Future studies should take this evidence into account in order to mitigate confounding factors.