Effects of treatment refractoriness and brain-derived neurotrophic factor Val66Met polymorphism on antidepressant response to low-dose ketamine infusion

Evidence suggests that levels of treatment refractoriness and brain-derived neurotrophic factor (BDNF) rs6265 polymorphism are related to the antidepressant effects of conventional antidepressants and repetitive transcranial magnetic stimulation. However, whether these factors are associated with the antidepressant effects of low-dose ketamine remains unclear. In total, 71 patients with treatment-resistant depression (TRD) were randomized to 0.5 mg/kg ketamine, 0.2 mg/kg ketamine, and saline control infusion groups. They were further divided into three treatment refractoriness groups according to the Maudsley staging method and were genotyped for Val66Met BDNF polymorphism. Participants' Hamilton Depression Rating Scale (HDRS) scores were assessed preinfusion, at 40, 80, 120, and 240 min postinfusion, and sequentially on days 2-7 and 14 after infusion. Patients with any Val allele exhibited an antidepressant response (p = 0.029) to 0.5 mg/kg ketamine vs. 0.2 mg/kg ketamine vs. saline control infusions. However, the trajectory of HDRS scores did not differ (p = 0.236) between the treatment groups among Met/Met carriers. In the low treatment refractoriness group, the 0.2 mg/kg ketamine infusion exhibited the optimal antidepressant effect (p = 0.002); in the moderate treatment refractoriness group, the 0.5 mg/kg ketamine infusion achieved the strongest antidepressant effect (p = 0.006); however, in the high treatment refractoriness group, the trajectory of depressive symptoms did not differ between treatments (p = 0.325). In future clinical practice, ketamine dose may be adjusted according to the level of treatment refractoriness and BDNF rs6265 polymorphism to achieve the optimal antidepressant effect for patients with TRD.