GSK3B and major depressive disorder: Mammalian target of rapamycin (mTOR), Ca2+/calmodulin-dependent protein kinase 2γ (Camk2γ) and glycogen synthase kinase-3β (GSK-3β) are three fundamental biomarkers implicated in the underlying mechanisms of depression, schizophrenia, mania and certain neuropsychiatric diseases (11–13).