Residual insomnia is the most common residual symptom after remission of depressive disorder and is an important marker for predicting recurrence and insufficient functional rehabilitation. Even when core depressive symptoms improve, difficulty falling asleep, nocturnal awakenings, early morning awakening, and non-restorative sleep may persist, closely linking to anxiety, reduced quality of life, and relapse risk. Thus, residual insomnia should be viewed as a clinical signal that the sleep-mood-circadian system has not yet fully stabilised. Electroacupuncture has been reported to modulate several sleep-related pathways, including the hypothalamic-pituitary-adrenal axis, melatonin secretion, core clock genes, and autonomic activity. However, the current evidence base, mostly derived from animal studies, indirect mechanistic reports, or non-residual-insomnia populations, is insufficient to prove that electroacupuncture reconstructs human circadian rhythms. Most clinical trials rely on subjective scales and lack objective phase markers such as dim-light melatonin onset, cortisol curves, actigraphy, or polysomnography. This article explicitly distinguishes between "subjective sleep improvement" and "objective rhythm reconstruction". We propose a testable research framework that stratifies residual insomnia by circadian phenotypes, uses electroacupuncture as a non-photic time cue, and combines timed intervention to evaluate rhythm-restoring effects. The traditional Midnight-Noon Ebb-Flow (Ziwu Liuzhu) theory is integrated into this chrono-electroacupuncture hypothesis as a heuristic tool for symptom-time recording and protocol design. Future research should adopt rigorous phenotyping, objective circadian biomarkers, and long-term follow-up to advance electroacupuncture from empirical sleep aid towards a precise rhythm-guided intervention.
