Night owls, delayed sleep phase and screens

If you can’t fall asleep until 2 a.m. no matter how tired you are, your body clock may simply run late. Light is what sets that clock, and screens are a big part of the light you see at night.

Updated October 8, 2026 · 2 min read

Key points

In a Norwegian study of teenagers, 3.3% met the criteria for delayed sleep phase syndrome, and over half of them also had insomnia.¹
Light in the evening pushes the body clock later; light in the morning pulls it earlier.²
Evening screen use delayed the body clock and sleep compared with reading a printed book.³
Dim, low-blue light at night and bright light in the morning work together.

What is delayed sleep phase?

Delayed sleep phase syndrome, also called delayed sleep-wake phase disorder, means your body clock runs hours later than the schedule you need to keep. You can’t fall asleep until very late and you struggle to wake up for school or work, but when you can sleep on your own schedule, you sleep normally. It’s most common in teenagers and young adults. In a large Norwegian study of 16- to 18-year-olds, 3.3% met the criteria, and more than half of them also had insomnia.¹

How does light shift your body clock?

Your body clock resets itself every day based on light. When researchers mapped how single pulses of bright light moved people’s clocks, light in the evening and early night shifted the clock later, while light in the early morning shifted it earlier.²

That’s why late-night light is a problem for night owls: it pushes a late clock even later. Blue-rich light does it most strongly.⁴

Do screens make delayed sleep worse?

In a sleep-lab study, reading on a light-emitting e-reader before bed for several nights delayed people’s body clocks, lowered melatonin and made them take longer to fall asleep, compared with reading a printed book.³ Even ordinary room light before bed delays melatonin.⁵

Who else runs late?

Late body clocks are especially common in adults with ADHD. In one study, 78% had chronic trouble falling asleep, with melatonin arriving later in the evening.⁶ See ADHD and screens.

Light habits that help night owls

Get bright light, ideally daylight, soon after you wake up.
Dim the lights and screens in the last few hours before bed.
Use warm, low-blue light in the evening.
Keep your wake-up time consistent, even on weekends.
If it’s affecting school, work or health, ask a doctor about treatment; options include timed light therapy and melatonin.

The Firelight isn’t a medical device or a sleep treatment. If a late body clock is affecting your life, talk with a doctor or sleep specialist.

Sources

Sivertsen B, Pallesen S, Stormark KM, et al.. Delayed sleep phase syndrome in adolescents: prevalence and correlates in a large population based study. BMC Public Health. 2013;13:1163. doi:10.1186/1471-2458-13-1163
Khalsa SBS, Jewett ME, Cajochen C, Czeisler CA. A phase response curve to single bright light pulses in human subjects. Journal of Physiology. 2003;549(3):945–952. doi:10.1113/jphysiol.2003.040477
Chang AM, Aeschbach D, Duffy JF, Czeisler CA. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. PNAS. 2015;112(4):1232–1237. doi:10.1073/pnas.1418490112
Brainard GC, Hanifin JP, Greeson JM, et al.. Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. Journal of Neuroscience. 2001;21(16):6405–6412. doi:10.1523/JNEUROSCI.21-16-06405.2001
Gooley JJ, Chamberlain K, Smith KA, et al.. Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. Journal of Clinical Endocrinology & Metabolism. 2011;96(3):E463–E472. doi:10.1210/jc.2010-2098
Van Veen MM, Kooij JJS, Boonstra AM, Gordijn MCM, Van Someren EJW. Delayed circadian rhythm in adults with attention-deficit/hyperactivity disorder and chronic sleep-onset insomnia. Biological Psychiatry. 2010;67(11):1091–1096. doi:10.1016/j.biopsych.2009.12.032