Cortico-limbic network dysfunction and genetic polymorphism are considered to be associated with major depressive disorder (MDD). Using diffusion tensor imaging (DTI), we investigated the relationship between catechol-O-methyltransferase (COMT) gene polymorphisms and white matter tract integrity in patients with MDD. Eighty-six patients with MDD and 62 healthy controls participated in this study. DTI and genotyping for the COMT val158met gene (rs4680) polymorphism were conducted to determine the impact of COMT polymorphisms on white matter changes in patients with MDD. Voxel-wise statistical analyses of fractional anisotropy (FA) were performed using tract-based spatial statistics (TBSS). FAs of the MDD patient group were significantly decreased in bilateral frontal forceps minor, bilateral anterior cingulum, genu of corpus callosum, left posterior cingulum, right superior longitudinal fasciculus, and right posterior thalamic radiation compared with those of healthy controls. In the MDD patient group, mean FA in subjects with the GG allele was significantly decreased in left inferior longitudinal fasciculus, bilateral middle temporal gyrus, right frontal gyrus, and right cingulum bundle area compared with subjects with the AA/AG allele. These findings suggest cortico-limbic network dysfunction in MDD. Specifically, further FA reduction was evident in MDD patients with the valine homozygote group of the COMT gene. MDD may be associated with dysfunctional white matter changes, and the valine homozygote of COMT gene may contribute to further abnormalities in these pathological changes.
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