Screen Time and Sleep—It’s Different for Adults

By Mary Grace Descourouez, MS, NBC-HWC

Many of us have heard that looking at our phones or iPads at night can keep us awake due to light exposure, however, research shows this may be true for children, but there is not sufficient evidence to support this claim for adults.

“Young children have a greater sensitivity to light because more light gets to the retina of a child than an adult,” says Jamie Zeitzer, PhD, Co-Director of the Stanford Center for Sleep and Circadian Sciences. “Since adults have more opacities in their eyes and smaller pupils than children, less light passes through adult eyes, so there’s less of an effect on melatonin production.”

Melatonin is a hormone that makes us feel sleepy and is released when the eyes perceive darkness. Conversely, when we see natural light in the morning, we feel more awake because light hitting our eyes stops the production of melatonin.

Given this logic, it would seem reasonable that looking at our screens (smart phones, computers, iPads, etc.) at night could delay melatonin production and inhibit our ability to fall asleep, but Dr. Zeitzer says this is not the case.

While darkness enables melatonin production, suppressing melatonin production works by the brain comparing the amount of light we receive during at night with how much we received during the day. It’s the shift from light to dark that cues the release of melatonin, which is why we start to feel sleepy after the sun goes down.

Since natural sunlight emits 10,000-100,000 lux of light and phone screens emit 25-50 lux under usual conditions at night, Dr. Zeitzer says the light from our screens doesn’t have much of an impact on the melatonin cueing process.

“There just isn’t that much light coming from your phone,” says Dr. Zeitzer. “As long as you go outside during the day and get exposed to the intensity of natural light then the amount of light from a screen in the evening most likely won’t halt the production of melatonin.”

If it’s Not Light, What Keeps us Up at Night?

Rather than light exposure, Dr. Zeitzer believes that what is keeping us awake is what we are watching on our screens. Millions of Americans stay awake at night scrolling on social media looking at page after page of emotionally activating content and writing posts that lead to likes, comments, and followers. Others stay up to play games on their phones or computers, all of which stimulate the dopamine reward system in the brain, which is the basis of addictive behaviors.

“In the past, when a television show ended, you turned off the TV and went to sleep because there was nothing else to do,” says Dr. Zeitzer. “But now you could watch Netflix, look at apps or play computer games all night because this entertainment has been commodified to engaged with it for as long as possible; it’s optimized to never stop playing and this is causing sleep deprivation.”

When watching screens before bed, Dr. Zeitzer recommends that we not only avoid content that could be distressing, but also content that could stir excitement within us.

“In order to fall asleep, we need to reduce stimuli exposure and calm our mind and body,” says Dr. Zeitzer. “Even if you’re watching something positive, if it stirs excitement, the brain will release dopamine, and over time we can develop a dopamine addiction, making staying awake playing games or on social media much more fun that going to sleep.”

Lastly, Dr. Zeitzer says that he can’t make a general statement that nighttime screen use negatively affects everyone’s sleep. For some, their addiction to games or apps could make falling asleep a challenge, while others may watch soothing nature videos on their phones to help them relax and fall asleep. Therefore, Dr. Zeitzer suggests that you take note of how screens are impacting your sleep health by asking yourself these questions:

• Is the content of your screen time making you feel distressed or excited? If yes, then you should not look at screens for about an hour before bedtime to calm the mind and body and prepare for sleep.
• Also, do you engage with screens throughout the night when you could be sleeping? If so, you may have a dopamine addiction that is making screen time activities more enjoyable than sleep.