BackgroundMajor depressive disorder (MDD) is a heterogeneous mental disorder having a very diverse course and causing a significant changes in daily life. Though the exact pathophysiology of depression is still not known, an alteration in the serum levels of cytokines and neurotrophic factors was seen in MDD subjects. In this study, we compared the serum levels of ‘pro-inflammatory cytokine leptin and neurotrophic factor EGF’ in healthy controls (HCs) and MDD patients. To make the findings more accurate, we eventually looked for a correlation between altered serum leptin and EGF levels and the severity of the disease condition.MethodsFor this case-control study, about 205 MDD patients were enrolled from the Department of Psychiatry, Bangabandhu Sheikh Mujib Medical University, Dhaka, and about 195 HCs were enrolled from various parts of Dhaka. The DSM-5 was utilized to evaluate and diagnose the participants. The HAM-D 17 scale was used to measure the severity of depression. After collecting blood samples, they were centrifuged to produce clear serum samples. These serum samples were analyzed using enzyme-linked immunosorbent assay (ELISA) kits to measure serum leptin and EGF levels.ResultsWe observed lowered serum EGF levels in MDD patients compared to HCs (524.70 ± 27.25 pg/ml vs. 672.52 ± 49.64 pg/ml,p= 0.009), and HAM-D score was elevated in MDD patients compared to HCs (17.17 ± 0.56 vs. 2.49 ± 0.43,p<0.001). But no correlation was established between serum EGF levels and the severity of depression. However, no significant differences were observed between MDD patients and HCs in the case of serum leptin levels (p= 0.231).ConclusionOur study findings suggest that reduced serum EGF levels have an impact on the pathogenesis of depression. But as per our investigation, the severity of depression is not correlated with altered EGF levels. Our findings regarding the association of EGF with MDD would help to use EGF as a risk indicator of depression. We suggest further clinical investigations to determine the precise function of leptin and EGF in depression.