The effects of 5-HTTLPR and BDNF Val66Met polymorphisms on neurostructural changes in major depressive disorder.

The serotonin-transporter-linked polymorphic region (5-HTTLPR) and brain-derived neurotrophic factor (BDNF) Val66Met polymorphism have been implicated in the pathophysiology of major depressive disorder (MDD). We aimed to investigate the effects of genetic variants of the 5-HTTLPR and BDNF Val66Met polymorphisms and their interactions with MDD on cortical volume and white matter integrity. Ninety-five patients with MDD and 65 healthy participants aged 20-65 years were recruited. The subjects were genotyped for the 5-HTTLPR and BDNF Val66Met polymorphisms and scanned with T1-weighted and diffusion tensor imaging. The gray matter volumes of 24 gyri in the prefrontal and anterior cingulate cortices and the fractional anisotropy values of nine white matter tracts in both hemispheres were determined. In the pooled sample of subjects from both groups, 5-HTTLPR L-allele carriers had significantly decreased cortical volume in the right anterior midcingulate gyrus compared to S-allele homozygotes. A significant effect of the interaction of the BDNF Val66Met polymorphism and MDD on the fractional anisotropy values of the right uncinate fasciculus was observed. Our results suggested that these genetic polymorphisms play important roles in the neurostructural changes of emotion-processing regions in subjects with MDD.