Circadian dimensions in insomnia disorder: mechanistic evidence, candidate phenotypes, and a phenotype-stratified research framework
Abstract
Insomnia disorder is one of the most common sleep disorders and is traditionally conceptualized in terms of hyperarousal, altered sleep homeostasis, and cognitive-behavioral perpetuating factors. The two-process model of sleep regulation indicates that sleep initiation and maintenance depend not only on homeostatic sleep pressure but also on circadian phase, amplitude, and stability. Evidence suggests that some patients presenting with insomnia complaints have misalignment between endogenous circadian phase and the intended sleep window, whereas others show reduced rest-activity amplitude, increased sleep-timing variability, or abnormal light exposure patterns. This narrative review integrates clinical, measurement, mechanistic, and intervention evidence on circadian dimensions in insomnia disorder and proposes a candidate circadian phenotyping framework for future validation. The framework combines sleep diaries, actigraphy, light exposure assessment, dim-light melatonin onset (DLMO), and core body temperature rhythms to distinguish circadian rhythm sleep-wake disorder (CRSWD)-dominant insomnia complaints, insomnia disorder with circadian modifiers, and comorbid insomnia disorder and CRSWD. Cognitive behavioral therapy for insomnia (CBT-I) remains first-line treatment. Fixed wake time, morning light, evening light restriction, timed low-dose melatonin, scheduled activity, and multicomponent approaches are positioned as candidate adjunctive modules to be tested in…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design.
Read the paper
Related studies
- Tryptophan Metabolism and Gut-Brain Homeostasis
- Rationale for a Multi-Factorial Approach for the Reversal of Cognitive Decline in Alzheimer’s Disease and MCI: A Review
- Prioritized Research for the Prevention, Treatment, and Reversal of Chronic Disease: Recommendations From the Lifestyle Medicine Research Summit
- Relationship between sleep disorders and gut dysbiosis: what affects what?
- The role of CLOCK gene in psychiatric disorders: Evidence from human and animal research
- Genetic, Transcriptome, Proteomic, and Epidemiological Evidence for Blood-Brain Barrier Disruption and Polymicrobial Brain Invasion as Determinant Factors in Alzheimer’s Disease
Go deeper in Evidence Hub
Evidence Hub adds a study data sheet (design, sample size, evidence level, key numbers), an AI summary and a chat grounded in the paper's text.