The measurement of serum soluble interleukin-6 receptor (sIL-6R) levels can be used to identify patients with treatment resistant major depressive disorder (MDD). A retrospective study on the topic was conducted between September 2018 and December 2018 in Japan among patients with MDD without psychotic features and published in Neuropsychopharmacology Reports.

The investigators sought to elucidate the appropriate biomarkers for the identification of patients with treatment resistant MDD, recognizing that the serum level of this marker might prove to be useful in clinical settings. They hypothesized that with the knowledge that immune-inflammatory processes are involved in the pathogenesis of MDD, the potential exists for particular cytokine-related molecules to serve as biomarkers. The study evaluated the serum levels of tumor necrosis factor-α (TNF- α), IL-6, and sIL-6R following treatment with antidepressant therapy.

A total of 25 patients with treatment resistant MDD (mean age, 52.4±2.0 years; 52.0% women) and 17 remitted patients (mean age, 53.6±2.0 years; 64.7%) were enrolled in the study. Serum sIL-6R levels were significantly higher among patients with treatment resistant MDD compared with remitted patients (37.6 ng/mL vs 31.1 ng/mL, respectively; P =.015). In contrast, no significant differences in TNF-α (2.23 pg/mL vs 1.90 pg/mL; P =.593) or serum IL-6 (1.79 pg/mL vs 1.41 pg/mL; P =.443) levels were reported between the 2 groups.

Continue Reading

Related Articles

The results of this study suggest that serum sIL-6R concentrations might prove to be a reliable biomarker for detecting patients with treatment resistant MDD. The use of receiver operating characteristic analysis also confirmed serum sIL-6R levels to be the only predictable biomarker for differentiating those patients with treatment resistant MDD from those without the condition. Moreover, the use of multiple regression analysis and the Quick Inventory of Depressive Symptomatology-Self Report score also demonstrated that only serum sIL-6R levels could be used to clarify the severity of a patient’s MDD.

The investigators concluded that longitudinal studies are warranted in order to monitor patients’ serum sIL-6R levels from the onset of antidepressant therapy and thus identify those with treatment resistant MDD.


Yamasaki K, Hasegawa T, Takeda M. Serum level of soluble interleukin 6 receptor is a useful biomarker for identification of treatment-resistant major depressive disorder [published online March 12, 2020]. Neuropsychopharmacol Rep. doi: 10.1002/npr2.12100.