Other circadian rhythm disorders¶
Non-24 is one of a family of circadian rhythm sleep-wake disorders (CRSWDs). They share a common theme — sleep happening at the "wrong" time relative to the day — but differ in why, and that difference matters for diagnosis and treatment.
Not medical advice
These are community overviews, not medical advice or diagnostic tools. Any of these disorders can overlap with — or be mistaken for — others, and several can be the visible sign of a different underlying condition. Diagnosis belongs with a qualified clinician.
Two broad groups¶
A useful first split is whether the body clock itself is at fault, or whether the clock is roughly normal but fighting the schedule it's been given:
- Intrinsic — the internal clock runs at the wrong phase (too late, too early) or the wrong period (not 24 hours), or loses its rhythm altogether. Delayed and advanced sleep phase disorders, Non-24, and irregular sleep-wake rhythm disorder are intrinsic.
- Extrinsic — the clock works, but an external schedule is misaligned with it. Shift work disorder and jet lag are the classic examples.
The line isn't always clean. Delayed sleep phase disorder can tip into Non-24; and someone with an intrinsic disorder forced onto a fixed timetable ends up in a state much like chronic, self-imposed shift work.
The family at a glance¶
| Disorder | What the clock is doing | Typical pattern |
|---|---|---|
| Delayed sleep phase (DSPD) | Runs late, but stable | Falls asleep very late, wakes late — every day |
| Advanced sleep phase (ASPD) | Runs early, but stable | Falls asleep in the early evening, wakes very early |
| Non-24 | Not locked to 24 h | Sleep drifts later (or, rarely, earlier) each day |
| Irregular sleep-wake (ISWRD) | Little or no rhythm | Sleep scattered in several bouts, no main night sleep |
| Shift work disorder | Normal clock, wrong schedule | Insomnia and sleepiness driven by work hours |
Explore¶
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Delayed & advanced sleep phase
Stable but shifted clocks — late (DSPD) or early (ASPD), and how DSPD relates to Non-24.
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Irregular sleep-wake rhythm
A rhythm so weak there's no main sleep — often a downstream sign of another condition.
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Shift work disorder
A normal clock at odds with night or rotating shifts.
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Non-24
The site's main focus: a clock that won't hold to 24 hours.
See also¶
- Circadian rhythm & zeitgebers — the groundwork for all of these
- Diagnosing Non-24 — much of the diagnostic logic (sleep diaries, actigraphy, ruling out look-alikes) applies across the family
- Circadian Sleep Disorders Network — definitions
Contributions welcome
These pages are starting points. Clinician-reviewed detail and good sources for each disorder are very welcome — contribute here.