An Observational Case-control Study for BDNF Val66Met Polymorphism and Serum BDNF in Patients with Major Depressive Disorder (MDD)

Background: The brain-derived neurotrophic factor (BDNF) has an important role in the growth of neurons and synaptic transmission. The BDNF gene Val66Met polymorphism (G/A) is associated with depression, but findings have not been consistently replicated. This study adopts a case-control design with an aim to investigate the association of Val66Met polymorphism and peripheral BDNF (serum) levels in patients of major depressive disorder (MDD) and healthy individuals (controls). Materials and Method: This study adopts an observational, case-control design with a total of 174 participants. Cases (n = 87) were currently depressed, having Diagnostic and Statistical Manual of Mental Disorders (DSM-5) MDD, without psychiatric comorbidity. Controls (n = 87) comprised healthy individuals with no family history of psychiatric illness. The cases were evaluated using the NIMH-Life Chart Method, Hamilton Depression Rating Scale (HAM-D), Clinically Useful Depression Outcome Scale (CUDOS), and Clinical Global Impression (CGI). TaqMan assay was used for genotyping, and serum BDNF was measured using Enzyme-linked immunosorbent assay (ELISA). Results: The case mean age was 35.32 +/- 11.69 years (52% females) and comparable to controls. Allelic distribution was 33% (Met), and genotypic distribution was 17% (Met/Met), 32% (Val/Met), and 51% (Val/Val) for cases. The genotypic distribution did not differ across study groups. Serum BDNF was significantly lower in MDD cases as compared to controls (p < .001). The serum BDNF levels were comparable across the genotypic groups among cases. Conclusion: The Val66Met polymorphism has not been associated with a risk for MDD and, interestingly, did not influence the BDNF levels (serum). Significantly low BDNF levels were found in MDD cases. The study findings show that factors other than Val66Met gene polymorphism have a role in modulating serum BDNF levels.