Since HCN channels were first reported to regulate the rhythm of myocardial sinoatrial nodal cells [18], HCN channels have subsequently been identified as widely expressed in the central and peripheral nervous systems; they appear to be critical to a series of physiological processes and pathological diseases—including pain [19], depression [20], epilepsy [21], and learning and memory [22]. This evidence concerns the gene MALAT1 and depressive disorder.