Objective: To determine whether the serotonin transporter (5-HTT) and norepinephrine transporter (NET) gene polymorphisms were associated with the susceptibility to depression.
Methods: Five hundred and seventy-nine patients with depression, evaluated using a 17-item Hamilton Depression Rating Scale for Depression (HAMD), and 437 healthy controls, all of Chinese Han origin, were genotyped by polymerase chain reaction.
Results: Both genotype distributions (P=0.033) and allele frequencies (P=0.023, OR = 1.250, 95% CI = 1.031-1.517) of NET-T182C were significantly different between patients and controls, where the T allele was associated with the onset of depression. Both NET-T182C T- and 5- HTTLPR L-carriers had higher baseline HAMD scores (P=0.032 and 0.023, respectively). There was an interaction between NET-T182C and 5-HTTLPR, where the combined genotype distributions were associated with both onset of depression (P=0.006) and the baseline HAMD scores (P=0.007).
Conclusion: This study suggested a positive relationship between the NET-T182C polymorphism and the susceptibility to depression, and a positive relationship between NET-T182C/5-HTTLPR polymorphisms and the severity of depression.