Key Findings
A cross-sectional study in Poland found that unmedicated patients with both major depressive disorder (MDD) and obesity have significantly higher circulating levels of acylated and deacylated ghrelin compared to non-depressed individuals with obesity.
The study included 31 patients with MDD and obesity and 31 control subjects with obesity, all of whom had not taken psychiatric medications for at least 12 months.
Adjusted analyses showed that MDD was an independent predictor of higher ghrelin levels for both forms, with a stronger effect for acylated ghrelin (p < 0.001) than deacylated ghrelin (p = 0.011). The ratio of acylated to deacylated ghrelin did not differ significantly between groups (p = 0.072).
Background
Major depressive disorder and obesity frequently co-occur, and each condition increases the risk for the other. Ghrelin, a hormone that regulates appetite and can cross the blood-brain barrier, influences dopamine pathways and stress processing.
Previous research on ghrelin in depression has yielded conflicting results, partly because it often measured total ghrelin rather than distinguishing between its two forms.
Methodology
Participants were recruited in Warsaw, Poland. Blood samples were collected after an overnight fast of at least 10 hours, with protease inhibitors added to prevent ghrelin degradation. Ghrelin concentrations were measured using enzyme-linked immunosorbent assay (ELISA) kits. Depressive symptoms were assessed using the Patient Health Questionnaire-9, and MDD diagnoses were confirmed via the Mini-International Neuropsychiatric Interview.
Conclusions
The authors suggest that elevated ghrelin levels in depressed individuals with obesity may reflect a compensatory neuroendocrine response to chronic stress.
However, due to the cross-sectional design, causality cannot be determined. Longitudinal studies with larger samples are needed to assess ghrelin's potential as a biomarker for depression in patients with metabolic disorders.