Delayed sleep phase disorder

Also called delayed sleep phase syndrome

Key points about delayed sleep phase disorder

  • Delayed sleep phase disorder is a sleep problem where your body's internal clock (circadian rhythm) is shifted by 2 hours or more, causing problems with falling asleep and waking up at a normal time.
  • This affects how you function while you're awake.
  • It can occur at any age but it’s more common in teenagers and young adults and may make it hard to wake in time for school or work.
  • Treatment mainly involves improving sleep hygiene by changing your lifestyle and bedtime environment to get better quality sleep.
Teenager sleeping late
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  • Delayed sleep phase disorder (DSPD) is a sleep problem where your body's internal clock (circadian rhythm) is shifted by 2 hours or more, causing problems with falling asleep and waking up at a normal time.
  • People with DSPD go to sleep later and wake later even with a regular sleep schedule.
  • This affects how well they sleep, when they sleep and how they function while they're awake.
  • DSPD can occur at any age but it’s more common in teenagers and young adults, and may make it hard to wake in time for school or work.

Note: Delayed sleep phase disorder is also called delayed sleep phase syndrome.

People with DSPD fall asleep and wake later than they want to and later than is socially acceptable or later than usual sleep and wake times.

  • Sleep and wake times are delayed by at least 2 hours and may be delayed by up to 3 to 6 hours.
  • For example, they might not be able to go to sleep until 4 am and find it hard to wake up until the afternoon.
  • Usually a person with DSPD has no problem staying asleep, but will complain of being unable to fall asleep.
  • This often results in:
    • trouble waking up in the morning in time to go to work or school
    • extreme daytime drowsiness
    • trouble staying alert during the day.

DSPD is thought to happen when your internal clock (circadian rhythm) is out of sync with the environment. Your circadian rhythm is on a 24-hour cycle and lets you know when it's time to sleep and when it's time to wake. Cues in the environment (eg, light, darkness, eating and physical activity) influence the sleep-wake cycle.

Your body's circadian rhythm is controlled mainly by the hormone melatonin. Melatonin is made by the pineal gland in your brain and helps to control your body's sleep pattern and sleep-wake cycle. For most people, melatonin levels start to increase between 7pm and 11pm and reach their peak values (maximum sleepiness) between 2am to 4am. Melatonin production is suppressed by light.

With teenagers, DSPD may be due to biological reasons where the onset of melatonin begins about an hour later in teens than adults. Staying up late to do homework, watch TV, play online games or use the internet can make the sleep delay worse.

There's no specific test to diagnose DSPD. Diagnosis usually involves your healthcare provider asking you questions about your sleep patterns and sleep environment. You may be asked to keep a sleep diary to note when you go to bed, when you fall asleep, and when you wake and what you do in the evening before bed. This log helps your healthcare provider get a full picture of your sleep habits.

Sometimes an actigraph (wrist watch-like device) is used to measure your sleep-wake pattern for a period of 2 weeks. It records your movement and light to determine when you are asleep or awake.

The goal of treatment for DSPD is to shift your sleep-schedule to an earlier time and keep to it. Treatment usually starts with improving sleep hygiene (see below) and you may need to reset your sleep routine.

Bright light therapy in the morning

Research shows that bright light exposure, either through natural sunlight or from a light box, in the first 1 or 2 hours of the morning helps to re-set your circadian rhythm. With your circadian rhythm re-set, you should fall asleep earlier and wake up earlier.

It's important to note that the bright blue light from computer screens can lower your natural melatonin levels and stop you from feeling as sleepy at night. For this reason, you should avoid using your computer or other electronic devices for 1 hour before your planned bedtime, and set devices to limit the amount of blue light emitted. You should also avoid bright light during the evening hours.

Improving sleep hygiene

Sleep hygiene refers to your lifestyle routines and bedtime environment that make it easier or harder to get better quality sleep. Changes you can make to improve your sleep hygiene include:

  • Avoiding TV, computer screens and mobile phones for an hour or two before bed, as the artificial blue light interferes with your natural cues to sleep.
  • Not using your bed as a place for work or catching up on social media.
  • Making sure your bedroom is cool, dimly lit or dark and as quiet and comfortable for sleep as possible.
  • Getting enough exercise and light during the day – exercising outdoors early or in the middle of the day (but not too close to your bedtime).
  • Going to bed at the same time every night – it's important that you keep your bedtime and wake up time as constant as possible. Try not to have a big difference between your schedule on weekdays and weekends (no more than 2 hours). 
  • Creating your own bedtime ritual (eg, if you worry about things to do tomorrow, to write them down, making a hot, milky drink or taking a warm bath) and starting your ritual at the same time each night.
  • Reducing or avoiding caffeine, cigarettes and alcohol, especially in the evenings.

Read more tips to improve your sleeping habits and use the information and worksheet in Te Kete Haerenga and sleep to help you work on your sleep patterns and behaviours.

Melatonin supplements

Melatonin supplements may be used to readjust your body clock to the desired time by taking it in the hours before your bedtime. Talk to your healthcare provider about whether melatonin is an option for you. Read more about melatonin.


Delayed sleep phase syndrome(external link) American Thoracic Society, US


  1. Delayed sleep phase disorder(external link) Sleep Foundation, US, 2024(external link)
  2. Delayed sleep phase syndrome(external link) American Thoracic Society, US, 2019

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Credits: Healthify editorial team. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

Last reviewed: