Back to overview
Other people get up at 7 AM and function. You lie there thinking that getting up is one of the worst inventions in human history.
You finally fall asleep at midnight, wake up at 8 AM – and are still exhausted. In the evenings you finally come alive. Ideas come, energy comes, your brain runs. At 11 PM.
This isn't a habit. It's biology.
The circadian rhythm is your biological 24-hour clock. It controls when you get sleepy, when you wake up, when cortisol and melatonin are released.
In people with ADHD, this rhythm is often shifted – backwards. It's called Delayed Sleep-Wake Phase Disorder (DSWPD).
Melatonin – the hormone that makes you sleepy – arrives in ADHD on average 1.5 to 2 hours later than the population average. When others get tired at 10 PM, you're still fully active. When you finally sleep, it's long past midnight.
Bijlenga et al. (2019) showed in a large study that this shifted rhythm is directly linked to ADHD severity – the more pronounced the ADHD, the greater the shift. Not coincidence, not a lifestyle phenomenon.
The internal clock isn't uninfluenceable. It responds to external signals called zeitgebers (German for "time givers"). The three strongest:
Light. Morning daylight is the strongest zeitgeber of all. It signals to the brain: day has begun, melatonin down, cortisol up. Those who don't get light in the morning shift their rhythm further back.
Exercise. Physical activity, especially in the morning or early afternoon, helps set the rhythm earlier. Evening exercise does the opposite – it shifts things back.
Meals. When you eat influences peripheral clocks throughout your body. An early breakfast can help anchor the rhythm.
You don't just wake up in the morning. You fight. Every alarm tone is a challenge. Even after enough sleep, you feel foggy for the first hour.
And the rest of the world? Starts at 8 or 9 AM. School, work, appointments – all oriented around a rhythm that isn't yours.
This is structurally difficult. Not because you're not trying, but because your body simply has a different beat.
This doesn't happen overnight. But it does happen.
1. Morning light first thing
Right after waking: light. Open the window, go outside, use a daylight lamp. At least 10 to 20 minutes, ideally within the first 30 minutes. This is the single strongest lever.
2. Fix your wake time
Sleep onset is hard to force. Wake time isn't. Getting up at the same time every day – including weekends, even if you barely slept – forces the rhythm to settle earlier.
3. Melatonin at the right time
Not as a sleeping pill, but as a zeitgeber: a small dose (0.5 to 1 mg) taken about 2 hours before your target sleep time can shift the rhythm. Worth discussing with your doctor.
4. Reduce light in the evenings
From 8 or 9 PM: less bright light, blue light filters on screens, no overhead lighting. This gives melatonin production a chance to start earlier.
5. Make peace with your rhythm
Where possible: adjust work times, schedule appointments after 9 or 10 AM. Not always doable – but when it works, it helps. A rhythm that isn't constantly fighting your daily schedule is less exhausting.
Van der Heijden et al. (2005) studied children with ADHD and idiopathic chronic sleep onset insomnia. Result: sleep phase delay was common – and responded to melatonin treatment. Not in everyone, but in a relevant portion.
That matters: if your sleep problem is based on a biologically shifted rhythm, classic sleep hygiene tips can only help so much. You have to address the pacemaker itself – through light, timing, and where appropriate, targeted melatonin.
Your internal clock isn't broken. It ticks differently. And it can be adjusted.
---
Disclaimer: This article is for educational purposes and does not replace medical or therapeutic advice. Melatonin supplementation should be discussed with a doctor.
- Bijlenga, D., et al. (2019). The role of sleep timing in adult attention-deficit/hyperactivity disorder. *Sleep Medicine*, 45, 119–127. [PubMed](https://pubmed.ncbi.nlm.nih.gov/30817948/)
- Van der Heijden, K.B., et al. (2005). Idiopathic chronic sleep onset insomnia in attention-deficit/hyperactivity disorder: a circadian rhythm sleep disorder. *Chronobiology International*, 22(3), 559–570. [PubMed](https://pubmed.ncbi.nlm.nih.gov/16076654/)
- Kooij, J.J.S., & Bijlenga, D. (2013). The circadian rhythm in adult attention-deficit/hyperactivity disorder. *Journal of Sleep Research*, 22(3), 238–244. [PubMed](https://pubmed.ncbi.nlm.nih.gov/23575897/)
The Internal Clock in ADHD
Why your rhythm isn't broken – it just ticks differently
You're Not a Morning Grouch by Choice
Other people get up at 7 AM and function. You lie there thinking that getting up is one of the worst inventions in human history.
You finally fall asleep at midnight, wake up at 8 AM – and are still exhausted. In the evenings you finally come alive. Ideas come, energy comes, your brain runs. At 11 PM.
This isn't a habit. It's biology.
The Delayed Circadian Rhythm
The circadian rhythm is your biological 24-hour clock. It controls when you get sleepy, when you wake up, when cortisol and melatonin are released.
In people with ADHD, this rhythm is often shifted – backwards. It's called Delayed Sleep-Wake Phase Disorder (DSWPD).
Melatonin – the hormone that makes you sleepy – arrives in ADHD on average 1.5 to 2 hours later than the population average. When others get tired at 10 PM, you're still fully active. When you finally sleep, it's long past midnight.
Bijlenga et al. (2019) showed in a large study that this shifted rhythm is directly linked to ADHD severity – the more pronounced the ADHD, the greater the shift. Not coincidence, not a lifestyle phenomenon.
Zeitgebers: What Sets the Internal Clock
The internal clock isn't uninfluenceable. It responds to external signals called zeitgebers (German for "time givers"). The three strongest:
Light. Morning daylight is the strongest zeitgeber of all. It signals to the brain: day has begun, melatonin down, cortisol up. Those who don't get light in the morning shift their rhythm further back.
Exercise. Physical activity, especially in the morning or early afternoon, helps set the rhythm earlier. Evening exercise does the opposite – it shifts things back.
Meals. When you eat influences peripheral clocks throughout your body. An early breakfast can help anchor the rhythm.
What This Means in Daily Life
You don't just wake up in the morning. You fight. Every alarm tone is a challenge. Even after enough sleep, you feel foggy for the first hour.
And the rest of the world? Starts at 8 or 9 AM. School, work, appointments – all oriented around a rhythm that isn't yours.
This is structurally difficult. Not because you're not trying, but because your body simply has a different beat.
Strategies to Shift the Rhythm
This doesn't happen overnight. But it does happen.
1. Morning light first thing
Right after waking: light. Open the window, go outside, use a daylight lamp. At least 10 to 20 minutes, ideally within the first 30 minutes. This is the single strongest lever.
2. Fix your wake time
Sleep onset is hard to force. Wake time isn't. Getting up at the same time every day – including weekends, even if you barely slept – forces the rhythm to settle earlier.
3. Melatonin at the right time
Not as a sleeping pill, but as a zeitgeber: a small dose (0.5 to 1 mg) taken about 2 hours before your target sleep time can shift the rhythm. Worth discussing with your doctor.
4. Reduce light in the evenings
From 8 or 9 PM: less bright light, blue light filters on screens, no overhead lighting. This gives melatonin production a chance to start earlier.
5. Make peace with your rhythm
Where possible: adjust work times, schedule appointments after 9 or 10 AM. Not always doable – but when it works, it helps. A rhythm that isn't constantly fighting your daily schedule is less exhausting.
What Van der Heijden Showed
Van der Heijden et al. (2005) studied children with ADHD and idiopathic chronic sleep onset insomnia. Result: sleep phase delay was common – and responded to melatonin treatment. Not in everyone, but in a relevant portion.
That matters: if your sleep problem is based on a biologically shifted rhythm, classic sleep hygiene tips can only help so much. You have to address the pacemaker itself – through light, timing, and where appropriate, targeted melatonin.
Your internal clock isn't broken. It ticks differently. And it can be adjusted.
---
Disclaimer: This article is for educational purposes and does not replace medical or therapeutic advice. Melatonin supplementation should be discussed with a doctor.
Sources
- Bijlenga, D., et al. (2019). The role of sleep timing in adult attention-deficit/hyperactivity disorder. *Sleep Medicine*, 45, 119–127. [PubMed](https://pubmed.ncbi.nlm.nih.gov/30817948/)
- Van der Heijden, K.B., et al. (2005). Idiopathic chronic sleep onset insomnia in attention-deficit/hyperactivity disorder: a circadian rhythm sleep disorder. *Chronobiology International*, 22(3), 559–570. [PubMed](https://pubmed.ncbi.nlm.nih.gov/16076654/)
- Kooij, J.J.S., & Bijlenga, D. (2013). The circadian rhythm in adult attention-deficit/hyperactivity disorder. *Journal of Sleep Research*, 22(3), 238–244. [PubMed](https://pubmed.ncbi.nlm.nih.gov/23575897/)