Seasonal affective disorder is a recurrent form of depression following a seasonal pattern. In addition to well-established seasonal alterations in circadian regulatory mechanisms and changes in dopamine, norepinephrine and serotonin metabolism that contribute to symptom development, epigenetic processes have increasingly come into focus, as they represent a molecular link between the environment and gene expression. Epigenetic alterations in MAOA and SLC6A4 display sex- and season-dependent patterns as well as associations with sunlight exposure. These findings suggest that epigenetic processes may contribute to the link between seasonal factors and serotonergic neurotransmission, although the transferability of peripheral methylation data to central brain processes remains limited. In the long term, epigenetic markers may help to identify vulnerable individuals and support the development of personalized preventive strategies.