Non-24-Hour Sleep-Wake Rhythm Disorder (Non-24) is a circadian rhythm disorder

What is it?

Non-24-Hour Sleep-Wake Rhythm Disorder (Non-24) is a circadian rhythm disorder where an individual's internal body clock is not synchronised to the 24-hour light-dark cycle of the environment. Instead, their internal clock "free-runs" on its own natural cycle, which is typically slightly longer than 24 hours. This causes their sleep and wake times to drift later and later each day, eventually cycling completely around the clock over a period of weeks. This condition is most common in people who are blind and cannot perceive light cues to reset their internal clock daily.

Common Symptoms:

• A sleep schedule that predictably shifts later every single day.
• A recurring, cyclical pattern of sleep problems.
• Periods of severe nighttime insomnia (when their internal clock promotes wakefulness during the night).
• Periods of severe daytime sleepiness (when their internal clock promotes sleep during the day).
• A temporary period where they feel "in sync" before the drift continues.
• An inability to maintain a conventional sleep-wake schedule for more than a day or two.

Potential Solutions:

The goal of treatment is to "entrain" or lock the free-running body clock into a stable 24-hour rhythm. For blind individuals, this is often achieved with medication, such as a specifically timed melatonin receptor agonist prescribed by a doctor. For sighted individuals with Non-24, treatment involves a very strict and structured daily regimen of chronotherapy, including precisely timed bright light therapy upon waking, structured periods of darkness (light avoidance) in the evening, and sometimes a strict activity schedule.

When to see a specialist?:

Due to its complexity and the difficulty of treatment, Non-24 almost always requires a diagnosis and management plan from a sleep specialist or a chronobiologist. If you or someone you know has a constantly rotating sleep pattern that cannot be stabilized, seeking professional help is the essential first step to getting an accurate diagnosis and a tailored treatment plan.