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目的:探讨脑源性神经营养因子（brain derived neurotrophic factor, BDNF）基因多态性（Val66Met，rs6265）与首次发病未治疗抑郁症患者的大脑灰质体积的相关性。方法:采用3.0 T磁共振成像对41例抑郁症患者（患者组）以及44名性别、年龄与患者组相匹配的健康对照者（对照组）进行头部磁共振成像扫描，同时检测受试者的BDNF基因rs6265多态性。采用基于体素的形态学方法（voxel-based morphometry, VBM）建立全因子分析模型，分析诊断（抑郁症与健康）和基因型（Val/Val与Met）对全脑灰质体积的影响。结果:患者组与对照组rs6265基因位点多态性的基因型和等位基因频率差异均无统计学意义（χn 2=0.004、0.048，均n P>0.05）。诊断主效应脑区为左侧楔前叶（n F=3.702，n P0.05). Gray matter volume in the left precuneus (n F=3.702, n P<0.001), right middle temporal gyrus (n F=4.020, n P<0.001) and cerebellum vermis_4_5 (n F=3.836, n P<0.001) was larger in MDD patients than in the control group. BDNF genotype had effects on left fusiform gyrus (n F=-4.152, n P<0.001). BDNF genotype-diagnosis interaction was found to be associated with left anterior cingulate cortex (n F=-4.775, n P<0.001) and right anterior cingulate (n F=-3.795, n P<0.001). For participants with Val/Val homozygous, compared to HC group, the volume of left anterior cingulate was reduced in MDD patients (n F=-3.729, n P<0.001). For participants with the Met allele, compared to healthy controls, MDD patients showed significantly increased GMV in the left middle frontal gyrus (n F=4.317, n P<0.001), right inferior occipital gyrus (n F=4.744, n P<0.001), right supramarginal gyrus (n F=3.838, n P<0.001), and left median cingulate gyrus(n F=4.041, n P<0.001). Separately in MDD patients and the control group, the GMV did not differ between the Val/Val homozygous group and the Met allele group.n Conclusion:BDNF rs6265 alleles could be related to brain structural abnormalities in MDD patients, and could further explain the pathological mechanism of MDD.