Screen time before bed might not be that bad after all

It isn’t that black and white, some sleep experts now say.

Spurred by recent research, sleep scientists and doctors are rethinking the conventional wisdom. In some cases, they are backing away from dogmatic approaches such as cutting out screens two hours before bedtime. And they are questioning how much the dreaded “blue light" actually delays sleep.

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

For some of us, certain kinds of screen use—like watching a comforting episode of a TV show on our phone—might actually help us fall asleep.

Not everyone has a free pass to spend hours glued to their phone before bed. Some people might be more sensitive to blue light than others. And certain people won’t be bothered by engaging content, like videogames, while others will find that even reading a printed book keeps them up.

Sleep experts recommend a few strategies. Set a bedtime alarm to make sure your phone use doesn’t lure you to stay up too late. Opt for what is called passive content, like reading or watching a show, that doesn’t require you to interact with it. And keep a sleep journal to identify what works for you.

The blue-light blues

A recent review study examining a decade of research on technology and sleep found the link is more nuanced than previously thought.

“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," says Michael Gradisar, an Australian clinical psychologist who co-wrote the review published in the journal Sleep Medicine Reviews.

In the early 2010s, Gradisar himself was among a group of researchers who proposed that bright light from screens at night could delay the circadian rhythm, in a review published in the journal Sleep Medicine.

Over the years as the idea gained traction, Gradisar, who now works for sleep-tracking app company Sleep Cycle, decided to put it to the test. In one study, he and others examined teens who played games and watched videos before bed on iPads with three different levels of brightness: a bright white screen, a dim white screen and a bright white screen with an app to reduce its blue-light emissions.

Researchers found there wasn’t a significant difference: It took teens who used the bright screen an average of 3.3 minutes longer to fall asleep than those using the dim screen.

Another study looking at iPhone use in young adults detected no significant differences in sleep outcomes, such as how long it took people to fall asleep and how long they slept for, regardless of whether they used a phone with a less-blue display, a normal display or no phone at all.

“The evidence [against blue light] is not as strong as we once thought," says Royette T. Dubar, a developmental psychologist and director of Wesleyan University’s Sleep and Psychosocial Adjustment lab, who wasn’t involved in the research.

Blue-light emissions have been shown in various studies to suppress melatonin, a sleep-promoting hormone. But that might not have as great an effect on how long it takes the average person to fall asleep as once thought, researchers say. A nearly 10-minute delay related to screen use—found in one study about 10 years ago—was the longest reported in the recent review of sleep studies.

Sleep-research organizations still largely recommend people limit screen time before bed.

The National Sleep Foundation suggests people turn off screens at least one hour before bedtime. The American Academy of Sleep Medicine, which says it “recognizes the harmful impact of screens and technology use on sleep quality," recommends at least 30 minutes to one hour.

The do’s and don’ts

Do track your sleep habits. To figure out aspects of your sleep “personality," try keeping a log of your sleep for a week, including what technology you used for how long and how you felt the following day, advises Dr. Shalini Paruthi, a sleep medicine doctor and member of the American Academy of Sleep Medicine’s Emerging Technology Committee. Experiment based on what you find.

Do set a bedtime alarm reminding you when it is time to go to sleep. Sleep can suffer when we are having too much fun (or too much stress) with technology and lose track of time, delaying when we fall asleep.

Do turn off your phone notifications, so you don’t get woken or anticipate being woken.

Do get plenty of natural light during the day. Sunlight has a more powerful effect on our sleep cycle than small amounts of blue light from screens in the evening, says Dr. Michelle Jonelis, a sleep medicine physician in the San Francisco Bay Area.

Don’t choose overly stimulating content. People with sleep problems might benefit from turning on a sitcom they have seen many times, rather than more-stimulating content, like a new show that will leave you wondering what is likely to happen next, says Aric Prather, director of the University of California, San Francisco’s Behavioral Sleep Medicine Research Program.

Don’t assume one approach works for everyone. Harris, the clinical psychologist, advises some of her patients to keep all their tech outside the bedroom, while others get the all-clear to watch sitcoms.

Write to Alex Janin at alex.janin@wsj.com