Association between dopamine beta-hydroxylase 19-bp insertion/deletion polymorphism and major depressive disorder

Norepinephrine and dopamine mediate important aspects of several psychoses, including major depressive disorder (MDD). Dopamine beta-hydroxylase (DBH) catalyzes the conversion of dopamine to norepinephrine in central neurons and thus is critically involved in maintaining the transformational homeostasis. Functional polymorphisms have been reported in DBH gene, including a 19-bp insertion/deletion polymorphism (DBH5'-insertion/deletion (Ins/Del)) and a single nucleotide polymorphism (-1021C/T). The purpose of this study was to investigate whether there was an association between the two functional polymorphisms and MDD in a Han Chinese population. DBH5'-Ins/Del and -1021C/T polymorphism in promoter region of DBH gene was analyzed in 313 patients with MDD and 318 healthy subjects by using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis. The results showed statistically significant associations for genotypic distribution between the DBH5'-Ins/Del polymorphism and MDD (P = 0.007). Individuals with Del/Del genotype demonstrated a 1.72 times increased risk of MDD compared to those with insertion alleles (95% confidence interval (CI) 1.20-2.47, P = 0.003). Moreover, the Del/Del genotype was associated with poorer digital span and language scores than the insertion alleles in healthy subjects (P = 0.041 and P = 0.048, respectively). However, there was no association observed between the genotype and allele frequencies for -1021C/T and depression. Our data suggest that the DBH5'-Ins/Del polymorphism of the DBH gene may be associated with susceptibility to MDD in a Chinese population.