Insomnia is a sleep disorder with a high global incidence; its pathogenesis is complex, involving the interaction of genetic predisposition, environmental stress, and psychophysiological factors. Epigenetics is a molecular mechanism that affects gene expression through environmental interaction. DNA methylation and N⁶- methyladenosine (m⁶A) modification are epigenetic mechanisms triggered by environmental stress and other factors, resulting in lasting changes in gene expression; they are a molecular bridge connecting external triggers and intrinsic susceptibility to insomnia. This article aims to systematically consolidate the existing evidence on the association between DNA methylation and m⁶A modification and insomnia, explore the core mechanism of insomnia affecting the regulation of circadian rhythm and the expression of neurologically related genes, confirm specific epigenetic profile changes in patients with insomnia, and propose future research directions to promote the discovery of biomarkers and the translation of epigenetic therapies through multi-omics integration and longitudinal research.