Pharmacogenetic association of bi- and triallelic polymorphisms of SLC6A4 with antidepressant response in major depressive disorder

•Gender may confound the association of 5-HTTLPR with antidepressant response, but the modulation effect needs to be confirmed by pooling patient-level data.•There was huge heterogeneity in analysis of Asians and the interpretation of results to the Asians needs caution.•Only a small number of studies investigating the association of 5-HTTLPR/rs25531 triallelic polymorphism with response to antidepressants were included. The results were not stable enough and subgroup analyses were not available