Biological mechanisms underlying depression, epigenetics and their interplay (Review)

Depression is a prevalent mood disorder that heavily affects the quality of life of affected individuals. The pathogenesis of depression is relatively complex, with the existing hypotheses focusing on alterations in monoamine signaling, the dysfunction of the hypothalamus‑pituitary‑adrenal glands axis, and a deregulated immune response. Moreover, the effectiveness of currently used pharmacotherapy, which is mostly based on the monoamine hypothesis, is not satisfactory. The study of epigenetics, i.e., heritable, and stable structural and biochemical alterations of the chromosome that are not associated with DNA sequence alterations, may help to elucidate the molecular mechanisms underlying depression and the response of patients to antidepressants. Epigenetic mechanisms, such as DNA methylation, histone modifications and regulation by non‑coding RNAs appear to affect the disease pathogenesis and appear to play a crucial role in the functions of antidepressants. Therefore, research on the influence of epigenetics on depression may prove to be fruitful. The present review aims to accumulate all known information regarding the biological mechanisms underlying depression, epigenetics and the response of patients to antidepressants.