Association between eating attitudes and serum apelin levels in patients with major depressive disorder

Objective: The aim of this study was to evaluate, by comparing with healthy controls, the relationship between eating attitudes and eating-related psychometric characteristics and serum apelin levels in individuals diagnosed with Major Depressive Disorder (MDD). Materials and Methods: This cross-sectional study was conducted at the Psychiatry Outpatient Clinic and the Medical Biochemistry Laboratory of Balıkesir University Health Practice and Research Hospital between February 1, 2025 and August 1, 2025. A total of 109 participants were included (54 healthy controls, 55 MDD). All participants completed the Sociodemographic and Clinical Information Form, the Beck Depression Inventory (BDI), the Eating Attitudes Test-26 (EAT-26), the Emotional Eating Scale (EES), and the ORTO-11 scale. Serum apelin levels were measured by ELISA in venous blood samples obtained after 8–12 hours of fasting. Group comparisons, Spearman correlation analysis, and hierarchical linear regression models were used for statistical analyses. Results: The patient and control groups were similar in terms of age and sex (p>0.05). Significant between-group differences were found in income level and employment status (p<0.05). BDI scores were significantly higher in the patient group than in the control group (control: 3.9±2.5; patient: 26.1±11.9; p<0.001). EES and EAT-26 scores were also significantly higher in the patient group (p=0.012 and p=0.020, respectively). ORTO-11 scores were higher in the control group than in the patient group (p=0.018). Serum apelin levels were significantly higher in the patient group than in the control group (median [min–max]: control 1198.3 [785.7–3426.7] pg/mL; patient 1352.3 [590.7–4000] pg/mL; p=0.023). In the total sample, serum apelin levels showed a low but significant positive correlation with BDI scores (r=0.308; p=0.001); however, no significant associations were observed between apelin levels and scale scores when the patient and control groups were analyzed separately (p>0.05). In hierarchical regression analysis, group, BDI, sex, and apelin levels did not independently predict eating attitudes; after adding ORTO-11 and EES, the model became significant, and ORTO-11 was the only independent predictor of eating attitudes in the final model (p<0.001). Conclusion: The findings indicate that eating attitudes and emotional eating are more adversely affected in individuals with MDD compared to healthy controls, and that serum apelin levels are higher in the patient group. However, apelin levels were not directly associated with eating-related psychometric scales and did not independently predict eating attitudes. The fact that ORTO-11 was the strongest predictor of eating attitudes suggests that eating-specific cognitive control processes may be more determinative than biomarkers and overall depressive symptom severity. Keywords: Major Depressive Disorder, Depression, Eating Attitudes, Apelin, ORTO-11