Evening Light and Sleep
What experiments show about room light, screens and e-readers in the evening, their effects on melatonin and sleep, and where the evidence stops.
Content last updated . This page has not been medically reviewed.
Quick answer
Experiments in sleep laboratories show that light in the hours before bed can lower melatonin (the hormone that rises in the evening), delay the body clock and, in one trial, delay falling asleep. What is less clear is how much ordinary home use of phones, tablets or lamps changes sleep in everyday life. This page is information only and gives no brightness, color or timing settings.
Room light before bed
In a retrospective analysis of 116 healthy volunteers aged 18 to 30 living in a research center, those exposed to ordinary room light (under 200 lux) in the 8 hours before bedtime had suppressed melatonin and a later melatonin onset compared with dim light (under 3 lux). Melatonin lasted about 90 minutes less. [1] The authors note that this could potentially affect sleep, temperature regulation, blood pressure and glucose, but those links were not tested in that study. [1] Label: established in laboratory conditions for melatonin; insufficient evidence for long-term health outcomes from this study.Light-emitting e-readers
In a controlled comparison, people who read on a light-emitting e-book device before bed, compared with a printed book, took longer to fall asleep, felt less sleepy in the evening, secreted less melatonin, had later body-clock timing and were less alert the next morning. [2] The authors cite a representative survey of 1,508 American adults in which 90% used some type of electronics within an hour of bedtime at least a few nights a week. [2] Label: mixed to promising; it is one carefully controlled study on one kind of device, and results may differ by device, brightness and person.What the broader review says
A systematic review of 128 studies found that evening, night and morning light all affected the timing of melatonin. It also reported that blue light in the evening suppressed melatonin, that the effect was strongest at the shortest wavelengths, and that melatonin recovered within about 15 minutes after exposure ended. [3] The same review noted that many studies were small (39 of 128 had 10 or fewer participants) and that few involved children or older adults. [3] An international consensus report on indoor light for healthy adults says current patterns of light exposure do not support the body clock well for many people. [4]| Claim you may see | What the sources show | Label |
|---|---|---|
| Evening light lowers melatonin | Shown in laboratory experiments. [1][3] | established |
| Light-emitting screens delay sleep | One trial found delay with an e-reader. [2] | promising but limited |
| "Blue light" is the only problem | The review also found responses to red light and low light levels at night in experiments. [3] | mixed |
| A product fixes evening-light effects | See the product page; not established here. | marketing claim |
What is not shown here
- Benefit of a device. Showing that light changes melatonin is not proof that a product improves how you feel the next day.
- Glasses and filters. The studies above did not test blue-light-blocking glasses or screen filters. For what trials show, see blue-light-blocking products.
- Individual differences. Participants were mostly young adults. [3]
How to judge evening-light claims
- Check whether the study measured melatonin, sleep tracked by a device, or sleep measured in a lab.
- Be wary of "blue light ruins your sleep" or "this app fixes it" without a trial.
- Compare with morning light and the circadian rhythm, since the same light can have different effects at different times.
Frequently asked questions
Does blue light from my phone keep me awake?
In experiments, evening light, including short-wavelength light, suppressed melatonin. [3] One trial found a light-emitting e-reader delayed sleep compared with a printed book. [2] How much your own phone use changes your sleep is not settled by these studies.
Is room lighting also a problem?
In one analysis, room light before bed suppressed melatonin and shortened its duration compared with dim light. [1]
Does reading a printed book help?
In the e-reader trial, participants fell asleep sooner and secreted more melatonin when reading a printed book. [2] That is one study on one device.
Are children affected the same way?
Proper evidence not found in the sources read for this page. The systematic review noted that very few studies involved children. [3]
Do I need a sleep tracker to know?
No. A simple diary can show whether your sleep changes. See sleep tracker vs sleep diary.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
How to read the evidence labels
Labels used on this page: established, promising but limited, mixed, insufficient evidence, marketing claim.
Safety and who should check first
Sleep trouble that lasts, or daytime sleepiness that affects driving or work, deserves a clinician's attention, whatever your lighting. See insomnia, CBT for insomnia and sleep safety and when to get help. Practical bedtime habits are covered in sleep hygiene.
References
- Gooley JJ, et al. J Clin Endocrinol Metab. 2011 Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. Read 2026-10-22.
- Chang AM, et al. Proc Natl Acad Sci U S A. 2015 Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Read 2026-10-22.
- Tähkämö L, Partonen T, Pesonen AK. Chronobiol Int. 2019 Systematic review of light exposure impact on human circadian rhythm. Read 2026-10-22.
- Brown TM, et al. PLoS Biol. 2022 Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.