Moreover, in order to explore the potential targets for treatment-resistant depressive patients, emerging evidence from clinical trials supported the use of glutamate receptor modulators for the treatment of depression and these include non-competitive NMDA receptor antagonists such as ketamine, subunit (NR2B)-specific NMDA receptor antagonists, NMDA receptor glycine-site partial agonists and metabotropic glutamate receptor (mGluR) modulators [122]. This evidence concerns the gene GRIN2B and depressive symptom measurement.