Tehran University of Medical Sciences Current Journal of Neurology 2717-011X 17 3 2018 07 05 105 110 EN Shirin Farjadian Department of Immunology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran Bahareh Fakhraei Department of Psychiatry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran Zahra Niknam Iran Neurological Association, Tehran, Iran Mahboubeh Nasiri Allergy Research Center, Department of Immunology, Shiraz University of Medical Sciences, Shiraz, Iran Aslan Azad School of Pharmacy, International Branch, Shiraz University of Medical Sciences, Shiraz, Iran Mojtaba Farjam Noncommunicable Diseases Research Center, School of Medicine, Fasa University of Medical Sciences, Fasa, Iran Alireza Nikseresht Department of Neurology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran 2017 10 19 2018 05 14 Background: Multiple sclerosis (MS) is the most common neuroinflammatory disease in young adults. Anxiety and depression may predispose individuals to MS and flare-ups. Serotonin transmission is modified in some brain regions of patients with MS, and these changes may contribute to their psychiatric abnormalities. We studied the frequencies of common polymorphisms of the serotonin reuptake transporter (SERT) gene in patients with MS according to their psychological status. Methods: The 5-HTTLPR, rs25531, and STin2VNTR polymorphisms of the SERT gene were genotyped by polymerase chain reaction (PCR)-based methods in 100 patients with MS and 100 healthy controls. Results: There were no remarkable differences in SERT gene polymorphisms between patients with MS and healthy controls. Unlike the control group, 41% of the patients showed some degree of depression based on Beck Depression Inventory (BDI), but no association was observed between SERT gene polymorphisms after the patients were stratified by depression status. Conclusion: In addition to SERT gene polymorphisms, modulation of serotonin at the synapses may also be regulated by genetic variations in tryptophan hydroxylase type 2 and serotonin receptors. Further studies with functional brain imaging of the serotonergic system in patients with MS can provide information on the role of serotonin in this disease. https://ijnl.tums.ac.ir/index.php/ijnl/article/view/1424