Abbreviations: miRNA - microRNA, MDD - major depressive disorder, MDE - major depressive episode, HDRS - Hamilton rating scale for depression, PBMCs - peripheral blood mononuclear cells, SIRT1 - sirtuin 1, SSRI - selective serotonin reuptake inhibitor, SNRI - serotonin-norepinephrine reuptake inhibitor, CBT - cognitive behavioral therapy, ECT - electroconvulsive therapy. The gene discussed is SIRT1; the disease is depressive disorder.