Investigation of irisin levels in patients withmajor depressive disorder

Objective: Major depressive disorder (MDD) is not only a common psychiatric disorder but also an important public health problem due to the disability, individual and social costs it causes. MDD has a wide history spanning from classical antiquity to modern times. The difference observed in clinical presentation, unpredictable course, prognosis and variable responses to treatment increase studies on the biological basis of MDD. Endocrine, inflammatory and neuronal circuits are closely related in the pathophysiology of MDD. Our study aimed to evaluate the relationship between the first diagnosed MDD cases and the irisin. Method: This study was conducted with the cases who applied to Recep Tayyip Erdoğan University Training and Research Hospital Psychiatry Outpatient Clinic between on September 25 th, 2019-2020. Considering the inclusion and exclusion criteria, 85 patients and 81 healthy control group cases were included in the study. Patients included in the study were diagnosed with MDD after the Structured Clinical Interview Questionnaire for DSM-IV Axis I and II Disorders (SCID-I, II) and the Hamilton Depression Scale (HAM-D) were implemented. All the data obtained from the study were analyzed using the Statistical Packages for the Social Science (SPSS Inc., Chicago, IL, USA) 18 statistical package program. Findings: The relationship between sociodemographic data and measured parameters with irisin levels was evaluated. It was determined that patients with MDD had lower irisin levels compared to healthy controls. A statistically significant relationship was found between irisin levels and the Hamilton Depression Rating Scale. This relationship showed a statistically inverse correlation. The relationship between age and irisin levels was statistically significant. The presence of a negative correlation indicating that irisin levels decreased with increasing age was statistically significant. Result: In our study, we determined that irisin levels may be low in patients with MDD who were diagnosed for the first time, had no comorbidity and did not use any medication before. In our findings, there may be an inverse correlation between the clinical severity of patients with MDD and irisin levels evaluated by HAM-D scores. However, there are many factors that affect irisin levels. This study may emphasize a possible role of decreased serum irisin levels in MDD's biological background.The results of our study may support the investigation of irisin as a biomarker or therapeutic target associated with MDD. viii Keywords: Major Depressive Disorder, irisin, etiology, pathophysiology