Synopsis
Distinguish circadian misalignment from insomnia and insufficient sleep, document timing across work and free days, and use carefully timed behavioural, light and specialist treatments without worsening the phase.
- Circadian disorders are persistent mismatches between internal sleep timing and the schedule required by work, education, care or social life.
- In delayed sleep-wake phase disorder, sleep is late but often normal in duration and quality when the person follows their preferred schedule.
- Advanced sleep-wake phase disorder produces early evening sleepiness and early morning waking, again with better sleep on the preferred schedule.
- Use at least a two-week sleep diary covering work and free days; actigraphy can add objective timing but does not replace clinical interpretation.
- Morning bright light tends to advance the clock and evening light tends to delay it, but the response depends on biological timing and mistiming can worsen symptoms.
- Melatonin is a phase-shifting signal whose timing may matter more than sedation; circadian use often needs specialist advice and product-specific prescribing.
- Anchor wake time, morning activity, light, meals and exercise, then shift gradually while protecting adequate total sleep opportunity.
- Shift-work problems also require roster and fatigue-risk measures; individual sleep advice cannot remove an unsafe work system.
Key red flags
Sleep-related collision, near miss or irresistible sleep during driving requires immediate driving cessation and assessment of excessive sleepiness.
Reduced need for sleep, elevated mood, agitation or impulsivity after light or schedule change suggests hypomania or mania.
Snoring with apnoeas, cataplexy, dream enactment or stereotyped nocturnal events points to another sleep disorder needing specialist evaluation.
Sudden onset, neurological change, severe depression, suicidality or substance withdrawal should not be attributed to circadian preference alone.
Investigation priorities
Compare sleep onset, waking, naps, opportunity and impairment across required days, free days and different shifts.
Management branches
Sleep difficulty and daytime impairment vary strongly with clock time or schedule.
- Complete at least two weeks of diary data including free days, shifts, naps, light exposure and actual sleep opportunity.
- Ask whether sleep becomes normal on the preferred schedule and screen for insufficient sleep, insomnia, apnoea, hypersomnolence and mood elevation.
- Name the phase direction and functional goal before choosing any light, melatonin or schedule intervention.