Sažetak. Veliki depresivni poremećaj (MDD, od engl. Major Depressive Disorder) jedan je od najčešćih psihosomatskih poremećaja, sa snažnom tendencijom porasta broja oboljelih. Do 2020. godine mogao bi postati drugi najveći zdravstveni svjetski problem. Uzroci nastanaka bolesti, kao i klinička slika, vrlo su složeni. Ovakva složenost posljedica je aktivnosti velikog broja gena, od kojih svaki "pridonosi" nastanku i izražaju bolesti s relativno malim udjelom. Sve veći broj rezultata mnogih studija upućuje na važnost epigenetičkih mehanizama regulacije aktivnosti gena, kao poveznicu bioloških i drugih čimbenika koji se povezuju s nastankom depresije. Većina istraživanja pokazuje uzročno-posljedičnu vezu između različitih bioloških i psihosocijalnih čimbenika, s jedne strane, te međuovisne promjene obrazaca metilacije/demetilacije molekule DNK i promjene koda histona, s druge strane. Sve je više podataka o značajnoj ulozi različitih nekodirajućih molekula RNK u nastanku depresivnog poremećaja. Konačno, pokazalo se da mnogi antidepresivi djeluju na epigenom. Ovaj učinak otvara potpuno novo poglavlje u razumijevanju patogeneze i epigenetičke podloge liječenja depresivnog poremećaja.Ključne riječi: antidepresivi; epigenetika; stres; veliki depresivni poremećaj Abstract. Major Depressive Disorder (MDD) represents one of the most common psychosomatic disorders with a pronounced increasing incidence. It is expected to become the number two major world health problem by 2020. The causes of MDD as well as its clinical features are very complex. The probable reason for such complexity relates to a large number of genes, being involved in a condition where each gene makes only a minor contribution to the MDD etiology and clinic phenotypes. An increasing number of studies published during last decade have pointed out the importance of epigenetic regulatory mechanisms in affecting gene activity as well as constituting a possible link between biological and other factors related to MDD. Most of the studies have shown causality between different, MDD related biological and psycho-social factors. They have also described mutually controlled processes involved in the regulation of DNA methylation and establishment of histone code. There is a growing body of evidence on the significant role of non-coding RNA molecules in the ethiopathogenesis of MDD. Finally, it was shown that many antidepressive agents exert much influence on the epigenome. Such activity opens a new chapter in understanding the MDD pathogenesis and the basis for epigenome-reshaping related therapy.