Overview
Delayed sleep phase is a condition that affects the body's internal clock, known as circadian rhythm. People with delayed sleep phase have sleep patterns that occur two or more hours later than usual patterns. They go to sleep later and wake later. This makes it hard to get up in time for work or school. Delayed sleep phase also is known as delayed sleep-wake phase disorder.
A treatment plan might include making changes to sleep habits, taking melatonin supplements and using light therapy.
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Symptoms
Symptoms of delayed sleep phase include falling asleep and waking up later than usual. Sleep and wake times are delayed at least two hours and may be delayed up to 3 to 6 hours. For example, people with delayed sleep phase may regularly go to sleep at 3 a.m. and wake at 10 a.m.
Delays in sleep and wake times last at least three months and often for years. Symptoms may include:
- Not being able to fall asleep at a typical bedtime, known as insomnia.
- Trouble waking up in the morning in time to go to work or school.
- Extreme daytime drowsiness.
- Trouble staying alert during the day.
When to see a doctor
See a healthcare professional if you have persistent symptoms of delayed sleep phase. Or make an appointment for your child if you think your child has these symptoms and they don't go away.
Also make an appointment if you or your child regularly has trouble waking in the morning or has excessive daytime drowsiness.
Causes
Delayed sleep phase is caused by a person's internal clock being out of sync with the environment. Your internal clock lets you know when it's time to sleep and when it's time to wake. Known as circadian rhythm, your internal clock is on a 24-hour cycle. Cues in the environment influence the sleep-wake cycle. These cues include light, darkness, eating and physical activity.
The exact cause of delayed sleep phase isn't known. But circadian rhythms can be delayed in teenagers for biological reasons. Staying up late to do homework, watch TV or spend time online can make the sleep delay worse.
Risk factors
Delayed sleep phase can affect children and adults of any age. However, the condition is more common among teenagers and young adults.
Complications
Teenagers with delayed sleep phase can have complications, such as poor performance in school and behavior issues, including attention-deficit/hyperactivity disorder (ADHD). Delayed sleep phase also has been associated with autism spectrum disorder.
In teenagers and adults, it's common to have depression and anxiety along with this sleep condition.
Prevention
Some lifestyle changes can help prevent delayed sleep phase. Follow a regular, consistent bedtime schedule and limit bright light and screens before bed to help you sleep.
Feb. 27, 2026