en Rheumatology Rheumatology Original Research: Clinical Science Original Research: Clinical Science <p><strong>Background: </strong>Numerous studies have been conducted to evaluate the frequency of hypovitaminosis D in patients with fibromyalgia syndrome (FMS) and its association with FMS symptoms. This study aimed at assessing the effect of hypovitaminosis D on the symptoms and quality of life of patients with fibromyalgia.<br> <strong>Methods:</strong> A total of 74 FMS patients with hypovitaminosis D were randomly assigned into group A (Trazodone 25 mg at bedtime + vitamin D 50 000 IU weekly) and group B (Trazodone 25 mg at bedtime + placebo). Serum vitamin D level, Widespread Pain Index (WPI), Fibromyalgia Impact Questionnaire (FIQ), Pittsburgh Sleep Quality Index (PSQI), and Short Form Health Survey (SF-36) were used at the beginning of the treatment and 4 and 8 weeks post treatment.<br> <strong>Results: </strong>Significant improvements were observed in WPI, FIQ, and PSQI scores in both groups. Moreover, combination of vitamin D and Trazodone resulted in significant improvement of SF-36 scores compared to Trazodone therapy. Improvement in pain-related indices including the WPI and the physical component score (PCS) fraction of SF-36 was more noticeable in vitamin D/Trazodone combination therapy.<br> <strong>&nbsp;&nbsp; Conclusion:</strong> This study suggests that vitamin D supplementation has significant therapeutic benefits in the management of FMS, especially in pain reduction of patients with fibromyalgia. According to our results, a combination of vitamin D supplements and a conventional antidepressant, when given to vitamin D-deficient fibromyalgia patients, could significantly improve both physical and psychological symptoms.<br> &nbsp;</p> Fibromyalgia syndrome, Vitamin D, Pain, Quality of life 167 172 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-2649-2&slc_lang=en&sid=1 Alireza Mirzaei mirzaeialireza26@gmail.com 200319475328460037503 200319475328460037503 No Bone and Joint Reconstruction Research Center, Shafa Orthopedic Hospital, Iran University of Medical Sciences, Tehran, Iran. Mozhdeh Zabihiyeganeh Mozhdehzabihi@gmail.com 200319475328460037504 200319475328460037504 Yes Bone and Joint Reconstruction Research Center, Shafa Orthopedic Hospital, Iran University of Medical Sciences, Tehran, Iran. Seyed Adel Jahed adeljahed@yahoo.com 200319475328460037505 200319475328460037505 No Research Center for Prevention of Cardiovascular Diseases, Institute of Endocrinology and Metabolism, Iran University of Medical Sciences, Tehran, Iran. Elnaz Khiabani khiabani_e@yahoo.com 200319475328460037506 200319475328460037506 No Hematology- Oncology Department, Emam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran. Marzieh Nojomi mnojomi@gmail.com 200319475328460037507 200319475328460037507 No Preventive Medicine & Public Health Research Center, Department of Community Medicine, School of Medicine, Iran University of Medical Sciences, Tehran, Iran. Salman Ghaffari orthosalman@yahoo.com 200319475328460037508 200319475328460037508 No Bone and Joint Reconstruction Research Center, Shafa Orthopedic Hospital, Iran University of Medical Sciences, Tehran, Iran.