Is it the blue light or the scrolling that keeps you up?

For most people, what they do on a phone before bed probably matters more than the blue light coming off it. In two studies of healthy teenagers and college students using a phone or tablet for about an hour before bed, the screen's light made little or no measurable difference to how fast they fell asleep, while surveys keep linking late-night texting and other interactive phone use with worse sleep.

The research has real gaps, and almost none of it was done with people who have insomnia. We read it as a reason to put screens away about half an hour before bed and keep the phone out of bed altogether. Night Shift and other warm-color settings are fine to leave on. We just wouldn't rely on them.

What does blue light from screens do to sleep?

When the dose is big enough, blue light from screens can push the body clock later and hold back melatonin, the hormone that rises in the evening. The best-known study had 12 healthy young adults reading on an iPad for about four hours before bed, five evenings in a row, in an otherwise very dim room. After the iPad evenings they took about 10 minutes longer to fall asleep than after five evenings with printed books (26 minutes against 16). Their melatonin was lower in the evening, and they were less alert the next morning.

Most evenings look nothing like four hours on a tablet in a near-dark room. When a sleep lab gave 16 healthy teenagers an hour on a bright tablet before bed, they took no longer to fall asleep than with a dim screen or one running a blue-light filter.

A larger trial put 167 college students on one of three plans for a week: their iPhone in the hour before bed with Night Shift on, the same with it off, or no phone at all. Wrist trackers found no difference in sleep between the three groups. Only in an extra analysis, of students who already slept more than about 6.8 hours, did the no-phone group spend less time awake during the night.

Blue-light glasses haven't done much better. A 2023 Cochrane review found six small trials with 148 people that measured sleep, and their results disagreed. The reviewers rated the evidence as very low certainty.

Why might the scrolling matter more?

Scrolling and texting keep your mind working right up to the moment you stop. A message wants an answer, and there's always one more post. In the National Sleep Foundation's 2011 poll of 1,508 Americans aged 13 to 64, nine in ten used some kind of device in the hour before bed. People who used more interactive ones in that hour, like phones, laptops and game consoles, were more likely to say they had trouble falling asleep and woke unrefreshed. Watching TV and listening to music didn't show the same link.

A Belgian survey of 844 adults aged 18 to 94 found that six in ten took their phone into the bedroom. Texting or calls after lights out went with taking longer to fall asleep, and more phone use at bedtime went with higher insomnia scores. A phone also takes time from the night. Another video, and bedtime slides later.

Surveys like these can't say which comes first. A 2024 review by sleep researchers in Australia and Sweden argues that poor sleep and phone use feed each other. People who can't sleep often pick up the phone to fill the time, or to calm themselves down while they wait for sleep.

Does putting the phone away before bed help?

Putting the phone away 30 minutes before bed has been tested directly in one small trial. At a university in Shanghai, 38 college students with poor sleep-quality scores and a bedtime phone habit, none with another sleep disorder or on sleep medication, were split into two groups. For one group, the researchers set most of the phones to lock themselves half an hour before bed, every night for four weeks. By their own sleep diaries, that group went from about 31 minutes to fall asleep to about 18, and slept around 18 minutes longer. The other group barely changed. The students who cut back also felt less keyed up at bedtime.

That study was a pilot, nobody was blinded, and the students signed up because they wanted to cut back. We take it as an early, hopeful sign. With the light studies, it's the reason our habit asks you to put the phone away.

How to keep screens out of the last half hour

Choose a time about 30 minutes before you usually go to bed, and set a phone reminder for it. When it goes off, plug the phone in somewhere outside the bedroom. If it's your alarm, a cheap alarm clock solves that. If you need the phone close for safety, or for someone you care for, keep it face down and out of arm's reach, with only emergency calls allowed through. Your phone's Sleep or Do Not Disturb setting can hold messages and notifications until the morning.

That half hour needs something in it, or you'll drift back to the screen. Read a paper book or a magazine, or play a podcast from a speaker across the room. A shower or tidying the kitchen works too. A short wind-down routine fits here well.

Some evenings you'll forget, or a message can't wait. Answer it, then put the phone back on the charger.

What about using your phone in bed?

Keeping the phone out of bed is a separate habit, and for some people it matters more than the half hour before. Scroll under the covers most nights and bed gets tied up with being alert. Stimulus control, one of the best-studied parts of CBT-I, asks people to use the bed only for sleep and sex, and this is why.

The phone in bed matters most after you've woken up at night. Checking it at 3am shows you the time and usually hands you something to chew on. Our 3am guide covers what to do instead. If you've been awake a while and it's turning into a struggle, get up for a bit and do something calm away from the bed. Anyone at risk of falls, or taking something for sleep, can stay put and sit up against the pillows with a dim lamp on. With bipolar disorder or epilepsy, talk to your doctor before changes that could cut into your sleep.

How long before it helps?

Plan on two weeks before you decide whether it's working. In the one trial that tested it, the clearest change was in how quickly people fell asleep. Expect a few bad nights in there anyway.

How Goodmorrow coaches it

If you tell us on day one that your last hour before bed goes to screens, "No screens 30 minutes before bed" is often where we start. It can also turn up later, once your morning notes keep bringing up late screens. When the notes are about the phone in bed, we suggest "No screens in bed" instead.

We time the reminder off a rough bedtime. Your ring gives us one, or we ask you once. With a watch it's the time you usually fall asleep, so if sleep takes a while to come, the reminder can land after you're already in bed. For the first week it arrives about 35 minutes before bed, something like "Half an hour to bed. Time to put the screens away." After that we only send it when it's likely to help, say the day after you missed an evening. Early on we send a short lesson, "Your phone keeps you switched on more than its light does." Each morning we ask about the night before, and one tap marks it done.

Turn on Phone time in the app's Settings and we'll tick off any evening your phone stays mostly down from half an hour before your usual bedtime until 4am. Under 30 minutes on it still counts as down. For "No screens in bed", the count starts at bedtime. Only the minutes reach us.

On day 14 we go back over the two weeks with you. A ring adds its rough count of your minutes before sleep each night. With Phone time on, we also compare how long you were on the phone in the evenings before the habit and since.

Goodmorrow is a coach for habits, and it can't diagnose or treat anything. Three or more rough nights a week for three months is worth taking to a doctor. So are falling asleep in the day when you didn't mean to, legs that won't keep still once you lie down, or a partner noticing you stop breathing at night. A doctor can also help when the phone is how you get through anxious nights and the worry follows you through the day. If you're having thoughts of suicide or harming yourself, call or text 988 in the US, or your local emergency number.