en Endocrinology Endocrinology Original Article Original Article <span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="line-height:14pt"><b><i><span style="color:blue">Background</span></i></b><i><span style="color:blue">:</span></i> Melatonin, mainly regulating the body&#39;s circadian rhythm, may have protective effects against type 2 diabetes mellitus (DM2)-induced depression due to its antioxidant and regulatory impact in the pathogenesis of both DM2 and depression. This study aimed to find the association of serum melatonin levels with depression in DM2 patients.</span><br> <span style="line-height:14pt"><b><i><span style="color:blue">Methods:</span></i></b> A total of 50 DM2 patients were recruited in this retrospective cross-sectional study and divided into 25 patients with depression (DM2-DP) and 25 without depression symptoms (DM2-NDP). Depression was diagnosed using the Hospital Anxiety and Depression Scale (HADS) assessment. Fasting blood samples were collected and examined for the level of serum melatonin and other biomarkers. All statistical analysis was performed by SPSS software Version 22, and a p-value less than 0.05 was considered statistically significant for all tests.</span><br> <span style="line-height:14pt"><b><i><span style="color:blue">Results:</span></i></b> The depression score was significantly lower in DM2-NDP than DM2-DP (p< 0.001). The mean weight was significantly lower in the DM2-DP group (P= 0.021). Total cholesterol, triglyceride, and anxiety scores were higher, and the melatonin level was lower in DM2-DP. The correlation of melatonin levels was positive with age, DBP, HbA1C, FBS, and TG. In contrast, it was negative with male gender, BMI, diabetes duration, SBP, TC, family history of DM, depression score, and anxiety score. However, no significant differences were seen.&nbsp;</span><br> <b><i><span style="color:blue">Conclusion</span></i></b><i><span style="color:blue">:</span></i> Lower melatonin may be associated with depression and anxiety in patients with DM2. The serum melatonin level might be a strong predictor of depression in DM2 patients.</span></span> Melatonin, Diabetes mellitus, Type 2 diabetes mellitus, Depression 421 429 http://caspjim.com/browse.php?a_code=A-10-2642-2&slc_lang=en&sid=1 Neda Kazemipoor nedakazemipoor@gmail.com 100319475328460048912 100319475328460048912 No Department of Clinical Pharmacy, Faculty of Pharmacy, Tehran Medical Sciences Islamic Azad University, Tehran, Iran. Alireza Arefzadeh alireza.arefzadeh@gmail.com 100319475328460048913 100319475328460048913 No Department of Endocrinology, Farhikhtegan Hospital, Faculty of Medicine, Tehran Medical Sciences Islamic Azad University, Tehran, Iran. Davood Dalil davood.dalil92@gmail.com 100319475328460048914 100319475328460048914 No Student Research Committee, Faculty of medicine, Shahed university, Tehran, Iran Maryam Shiehmorteza davood.dalili@yahoo.com 100319475328460048915 100319475328460048915 Yes Department of Clinical Pharmacy, Pharmaceutical Sciences Branch, Islamic Azad University, Tehran, Iran. Seyyed Mohammad Hosseini seyyedmh1998@gmail.com 100319475328460048916 100319475328460048916 No Student Research Committee, Faculty of medicine, Shahed university, Tehran, Iran