Many adults with ADHD fall asleep very late and find mornings a struggle. For some, this is more than a habit. It can be a body clock that runs late, a pattern sleep specialists call delayed sleep–wake phase disorder (DSWPD).
Research consistently links ADHD with a later body clock. A 2017 review of 62 studies linked ADHD with being an "evening type". It also linked ADHD with later release of the sleep hormone melatonin, and later sleep onset. Sleep specialists list ADHD among the conditions that appear to raise the risk of DSWPD.
What helps is mostly about timing. That means a fixed wake-up time and light at the right time of day. For some people, it means melatonin taken at a set time on a doctor's advice. Melatonin is prescription-only in Ireland and the UK. If you take ADHD medication, dose timing is a question for your prescriber.
This article is about the body clock. For the wider picture, including medication side effects and other sleep disorders, see ADHD and sleep: why they so often overlap.
Preferring late nights is common and is not a disorder in itself. DSWPD is defined in the International Classification of Sleep Disorders (ICSD-3). The American Academy of Sleep Medicine (AASM), which publishes it, has released the draft chapter of its updated text (ICSD-3-TR).
It describes DSWPD as sleep and wake times that are habitually delayed, usually by more than two hours, compared with conventional times. All of the following must apply:
On holiday, many people with DSWPD sleep well, just late. The same text says sleep often does not start until between 1am and 6am, with waking in the late morning or afternoon when unrestricted.
If you sleep badly whatever the hour, something else may be going on. The AASM text notes that chronic insomnia often develops alongside DSWPD. Years of trying to sleep too early can build frustration and a sense of alertness in bed.
It also says adult DSWPD estimates hover around 1%. It is more common in teenagers and young adults. For the teenage body-clock shift, see the teenage brain and sleep.
The evidence comes mostly from small, clinic-based studies:
These studies show an association. They do not show that ADHD causes the delay, or the other way round. And late sleep does not always mean a late clock. The AASM text says more than 40% of people who meet the diagnostic criteria do not have delayed melatonin onset.
There is no single test. Assessment usually involves:
If you are on ADHD medication, a diary has a second use. NICE guideline NG87 tells clinicians to monitor sleep changes, for example with a sleep diary, and adjust medication accordingly.
Light is the body clock's strongest signal. The NHLBI says using a light box when you wake moves sleep and wake times earlier. It lists this for DSWPD. It also advises more daylight during the day, less artificial light at night and dim lighting before bed.
The NHLBI lists possible side effects of light therapy: agitation, eye strain, headaches, migraines and nausea. Ask your doctor first if you have an eye condition or take medicines that make you sensitive to light.
The AASM's 2015 treatment guideline could not make a recommendation on light therapy for adults with DSWPD, because of a lack of evidence. It did suggest light therapy with behavioural support for children and teenagers.
How light shifts the clock for travel and night work is covered in jet lag and shift work: what resets your sleep clock.
The word is used in two ways.
Classic chronotherapy means going to bed later each day, so sleep moves round the clock until it reaches the time you want. A 1981 study tried this in five people with delayed sleep phase. Average sleep onset moved from 4:50am to 12:20am. That is a very small study. The AASM's 2015 guideline made no recommendation on this kind of scheduling for adults, again due to lack of evidence. It is disruptive and is not something to attempt without specialist support.
In ADHD research, "chronotherapy" usually means timed melatonin, bright light, or both.
One Danish trial combined CBT for insomnia with chronotherapy. It enrolled 88 outpatients with depression, attention deficit disorder or bipolar disorder who had insomnia or a circadian rhythm disorder. Six individual sessions improved self-rated sleep quality and insomnia severity at six weeks, compared with one sleep hygiene session. Actigraphy and sleep diaries showed no significant difference between groups.
If insomnia has built up alongside a late clock, CBT-I is the standard first treatment for the insomnia part. See CBT-I: the sleep treatment with better evidence than any supplement.
Your body makes melatonin at night, and the NHS says it helps control how and when you sleep. Taken as a medicine at the right time, it can act as a signal that shifts the clock.
What the guidelines say:
The best-known ADHD trial is from Amsterdam (van Andel and colleagues). Adults with ADHD and delayed sleep phase took 0.5 mg melatonin, placebo, or melatonin plus morning bright light, for three weeks. Doses started three hours before each person's measured melatonin onset and moved one hour earlier each week.
So shifting the internal clock and actually sleeping earlier turned out to be separate problems. The authors concluded that intensive behavioural coaching would be needed as well.
None of this is dosing advice. Timing in trials was tailored to each person, and the right plan is one your doctor makes with you.
Where you live matters:
The NHS also says caffeine works against melatonin, and alcohol can affect how it works. For dose and timing research, see melatonin: the real dose-response evidence.
The AASM's 2015 guideline made no recommendation on sleep-promoting medicines for adults with DSWPD, because of a lack of evidence. The ICSD-3-TR draft warns that using alcohol, sedatives, sleeping tablets or stimulants to manage the symptoms can keep the problem going.
Stimulants can affect sleep. The NHS lists trouble sleeping as a common side effect of methylphenidate in adults. For trouble sleeping, it suggests taking the last dose more than 6 hours before bedtime. Slow-release forms are usually taken in the morning.
The picture is not one-sided. An Irish study followed 149 adults at a specialist ADHD clinic for 18 months. Stimulant use was associated with better sleep quality and lower odds of insomnia. It was an observational study, so it cannot show cause and effect.
Questions worth asking:
Do not change or stop ADHD medication on your own. How medication works in Ireland is in ADHD medication for adults in Ireland.
See your GP if late sleep has lasted three months or more and is affecting work, college or daily life. Go sooner if:
Bring two weeks of a sleep diary if you can.
If you are having thoughts of suicide: in Ireland, freephone Samaritans on 116 123 or text 50808. In the UK, call Samaritans on 116 123. In the US, call or text 988. If you are at immediate risk, call 112 or 999 (Ireland), 999 (UK) or 911 (US), or go to an emergency department.
It is not one of the diagnostic features of ADHD. But research consistently links ADHD with a later chronotype and later melatonin onset. Not everyone with ADHD has a late body clock.
The ICSD-3-TR draft describes DSWPD as a chronic condition. The clock may shift earlier with age. It also says people usually keep a preference for late hours even after treatment, and relapse is common.
That is not established. In the Amsterdam trial, melatonin alone modestly reduced self-reported ADHD symptoms. Melatonin with bright light did not, and the effect had gone two weeks after treatment stopped.
This article is general information, not medical advice. Talk to your GP, prescriber or pharmacist about your own sleep and medicines.
Reviewed by: Proco Team
Last updated: November 2026