Myth or fact

Is your phone what stops your melatonin?

Short answerSort of

By GyroscopeUpdated November 14, 20265 sources

Sort of. Screens do count, but the whole room does most of the work. In a 2011 study, ordinary room light in the hours before bed made melatonin start later in 99 percent of people, phone or no phone. And in a small 2016 study, people who’d had a bright day saw no change in their sleep or melatonin after two hours of reading on a tablet in the evening.

Why it seems obvious

The phone is the thing in your hand at 11pm, glowing at your face. Blue light gets a lot of headlines, and almost everyone does it. A survey cited in a 2015 study found 90 percent of American adults used some kind of electronics within an hour of bed at least a few nights a week.

It’s also the easiest thing to blame. You can put a phone in a drawer. It’s harder to notice that every light in the kitchen and living room has been on since dinner.

Noise at a party

Blaming the phone alone is like blaming one guest for the noise at a party. That guest is loud and standing right next to you. But the music, the kitchen and twenty other people are making noise too, and sending one guest home won’t make the room quiet.

Your eyes take in all the light in the room, and your brain’s clock adds it up.

What the studies found

Room light, 2011. A team at Brigham and Women’s Hospital and Harvard compared 116 adults aged 18 to 30 in room light, under 200 lux, with dim light, under 3 lux, for the 8 hours before bed. Room light made melatonin start later in 99 percent of them and shortened their melatonin night by about 90 minutes. No phones were needed for that.

An e-reader against a book, 2015. Researchers at the same hospital had people read in the hours before bed on a light-emitting e-reader or from a printed book. On the e-reader, people took longer to fall asleep, felt less sleepy in the evening, made less melatonin, had a later body clock and were less alert the next morning.

A tablet after a bright day, 2016. In Uppsala, Sweden, 14 people spent 6.5 hours in bright light, about 569 lux, during the day. Then they read a novel from 9 to 11pm, on a tablet one week and as a printed book the other. Their sleep and their evening melatonin were the same either way. The authors suggested that bright light during the day may protect against the effect of evening screens, and said larger studies need to check it.

Light at your eyes has been known to stop melatonin since 1980, when a brighter lamp shut it off in six people where ordinary room light hadn’t. Bright light also moves your clock, pushing it later in the evening and pulling it earlier in the morning.

The best case for blaming the phone

“The e-reader study is clear. Screens delay your clock and cut your melatonin.” It’s a real result, and that’s why the verdict is sort of. A bright screen held close to your face in a dark room is light at your eyes at an hour when light pushes your clock later.

But the 2016 study suggests how much the screen does depends on what your eyes got during the day, and the 2011 study shows the room alone can do the damage. Turning off the phone while the overhead lights blaze fixes a small part of the problem.

What to do, in order

1. Get daylight, especially within an hour of waking.
2. Turn off the overhead lights from your melatonin window to bed, and use lamps.
3. Keep the bedroom dark, or wear an eye mask.
4. Then deal with the screen. Brightness down, further from your face, or out of the room.

Light does the same job, harder has the full light plan, and the melatonin window tells you when to start dimming.