Is screen time before bed bad?

In previous studies, blue light emissions have been shown to suppress melatonin, a hormone that promotes sleep, and can disrupt our circadian rhythm.

However, that might not have as much of an effect on how long it takes the average person to fall asleep as previously thought, experts say. In one review of sleep studies from around 10 years ago, researchers found the longest reported delay related to screen use was 10 minutes.

"One has to ask, does 10 minutes really make a difference?" said Michael Gradisar, a clinical psychologist.

Gradisar co-wrote a review study recently published in Sleep Medicine Reviews that looked at a decade of research on sleep and technology and found that the link between the two is nuanced.

"It's an interaction between a person's vulnerabilities — and not everyone has these vulnerabilities — and the type of activity that they're performing on these devices," Gradisar said.

In one study, Gradisar and others examined teenagers who played games and watched videos before bed on iPads at three different brightness levels: a bright white screen, a dim white screen, and a bright white screen with an app reducing blue light emissions.

They found no significant difference between the three groups. It took the participants who used the bright screen an average of 3.3 minutes longer to fall asleep than those using the dim screen.

"If we stand back and look at all of the factors that can be harmful to our sleep, screens are overrated," Gradisar said.

A separate study analyzing iPhone use in young adults also found no significant difference in sleep outcomes, including how long it took people to fall asleep and how long they slept for, regardless of whether they used a display with less blue light, a normal display, or none at all.

"The evidence [against blue light] is not as strong as we once thought," said Royette T. Dubar, a developmental psychologist and director of Wesleyan University's Sleep and Psychosocial Adjustment Lab.

Some people may be more sensitive to blue light than others, experts noted. Some may even be bothered by engaging content like videogames, while others may find that even reading a book could keep them up.

"It is becoming more evident that the tech in and of itself isn't always the problem" said Shelby Harris, a clinical psychologist specializing in behavioral sleep medicine. "We need to figure out how to tailor the recommendations to the person."

How to sleep better

Christine Blume, a psychologist at the University of Basel's Centre for Chronobiology, said that while blue light itself isn't significantly impactful on a person's sleep rhythm, she still recommends that people reduce their exposure to short-wavelength light in general, regardless of its color.

"Our results support the findings of many other studies that the light-sensitive ganglion cells are most important for the human internal clock," Blume said. "Therefore, short-wavelength light — misleadingly often termed 'blue light' — should be reduced in the evening, for example by dimming computer screens and using a night-shift mode."

The National Sleep Foundation also still recommends people turn off screens at least one hour before bedtime, and the American Academy of Sleep Medicine (AASM) says it "recognizes the harmful impact of screens and technology use on sleep quality," recommending turning off screens at least 30 minutes to an hour before bed.

Shalini Paruthi, a sleep medicine doctor and member of AASM's Emerging Technology Committee, recommends keeping a log of your sleep for a week, including what technology you used, how long you used it for, and how you felt the following day.

Experts also recommend setting a bedtime alarm reminding you of when to go to sleep, turning off your phone notifications, and getting plenty of natural light during the day. According to Michelle Jonelis, a sleep medicine physician, sunlight can have a more powerful effect on our sleep cycle than small amounts of blue light in the evening.

And if you do choose to scroll on your phone at night, don't choose overly stimulating content. Aric Prather, director of the University of California, San Francisco's Behavioral Sleep Medicine Research Program, said that people with sleep problems may benefit from turning on a sitcom they've seen many times, rather than more stimulating content like a new show. (Janin, Wall Street Journal, 5/29; Wigle, New York Post, 5/30; Vassell, The Independent, 6/5)

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