Higher serum interleukin-12 levels are associated with the pathophysiology of major depressive disorder: A case-control study results

Major depressive disorder (MDD) is the fourth biggest health-related concern that dramatically impacts individuals' mental and physical health. Alteration of serum proinflammatory cytokine levels may take part in the development and progression of MDD. We aimed to explore and compare the role of interleukin-12 (IL-12) in MDD patients and healthy controls (HCs) and its involvement with the disease severity.

The present study included 85 patients and 87 age-sex matched HCs. A qualified psychiatrist utilized the diagnostic and statistical manual of mental disorders, fifth edition (DSM-5) criteria to diagnose patients and evaluate HCs. We applied the Ham-D rating scale to measure the severity of depression. Serum IL-12 levels were measured using ELISA kits.

We observed a notable increase in the serum levels of IL-12 in MDD patients compared to HCs (164.27 ± 10.18 pg/ml and 82.55 ± 4.40 pg/ml; p < 0.001). Moreover, we noticed a positive correlation between serum IL-12 levels and Ham-D scores in MDD patients (r = 0.363; p = 0.001). Receiver operating characteristic analysis showed a good predictive performance (AUC = 0.871; p < 0.001) at the cut-off point of 53.46 pg/ml for serum IL-12.

The current study findings support that IL-12 levels are involved with the pathogenesis and inflammatory process in MDD. At the same time, this involvement may make this cytokine eligible for the risk evaluation of MDD. However, we recommend further interventional studies to explore more accurate associations between IL-12 and depressive disorder.