Serum Cortisol, Nesfatin-1, and IL-113: Potential Diagnostic Biomarkers in Elderly Patients with Treatment-Resistant Depression

Aim: Treatment-resistant depression (TRD) affects approximately 30% of patients with major depressive disorder (MDD), especially elderly patients. As individuals with TRD are at an increased risk of committing suicide and pose a higher risk of relapse, early diagnostic biomarkers of TRD and a better understanding of the resistance mechanism are highly needed. This study aimed to determine whether serum cortisol, nesfatin-1, and pro-inflammatory cytokines can be used as biomarkers for the diagnosis of elderly patients with TRD. Methods: Thirty elderly patients with TRD were selected as the TRD group. Thirty elderly patients with MDD who were effectively treated with conventional antidepressants were selected as the non-TRD group. The baseline levels of serum cortisol, nesfatin-1, and pro-inflammatory cytokines were measured and compared, and their diagnostic values were evaluated using the receiver operating characteristic (ROC) curve method for discriminating patients with TRD from those without TRD. Results: Serum cortisol, C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) levels were significantly higher in the non-TRD and TRD groups than in the control group. Moreover, serum cortisol, CRP, TNF-alpha, and IL-6 levels in the TRD group were significantly lower than those in the non-TRD group. Furthermore, serum nesfatin-1 levels in the non-TRD group were significantly lower than those in the control and TRD groups, while the serum IL-113 levels in the non-TRD group were significantly higher than those in the control and TRD groups. Additionally, an ROC analysis revealed an area under the curve (AUC) of 0.929 for the combination of nesfatin-1 and IL-113 and an AUC of 0.956 for the combination of cortisol, nesfatin-1, and IL-113 in discriminating elderly patients with TRD from those without non-TRD. Conclusion: Serum cortisol, nesfatin-1, and IL-113 may be potential diagnostic biomarkers for discriminating elderly patients with TRD from those without TRD.