Does blue light actually impact your sleep?

The long-standing theory is that blue light from phones, laptops, and televisions suppresses melatonin, the hormone that signals drowsiness. "As a result, you feel more alert, making it harder to fall — and stay — asleep," Legaspi writes.

However, some researchers caution that the relationship between blue light and sleep isn't so straightforward, with research on the topic being mixed. Many older studies were smaller and conducted in carefully controlled laboratories, limiting how much they reflect real life.

While it's true that blue light can lower melatonin, current evidence, albeit limited, suggests that screen use is not always behind the decline, said Mariana Figueiro, a scientist at the Icahn School of Medicine at Mount Sinai who studies light and health.

According to Figueiro's research, "how long you use your device for, how close it is to your eyes and how bright it is may play a role," Legaspi writes. In a 2013 study, Figueiro found that using an iPad at full brightness for two hours caused a small dip in melatonin, but one hour of use made no difference. In 2014, she found that watching television from nine feet away had no effect, while a 2018 study showed that using an iPad at higher brightness suppressed melatonin more than using it at dimmer light.

Daylight exposure also seems to shape nighttime responses. People who get more sunlight during the day appear to be less sensitive to blue light later in the day. Some people are also naturally less sensitive. In a 2019 study, one participant required 40 times more light exposure to suppress melatonin than the most sensitive participant.

Separately, a 2022 review of 12 studies found that most of the studies showed no link between blue light and poor sleep, though a few did. Last year, the National Sleep Foundation concluded that there was not "enough evidence to demonstrate that blue light exposure from screen use before bed can impair sleep," Legaspi writes.

Why your screen habits matter more

If blue light isn't always to blame, researchers say attention should shift to how people use their devices. According to Lauren Hartstein, an assistant professor of psychiatry at the University of Arizona, some research suggests that what people do on their devices can have a big impact on their sleep.

Interactive activities, including playing video games, browsing social media, shopping, and gambling, appear the most disruptive. Daniel Buysse, a psychiatrist and professor at the University of Pittsburgh, also called out social media as being particularly concerning since it's designed to hold users' attention for as long as possible.

These behaviors stimulate the brain's reward system, making it difficult to disengage. As Hartstein put it, you can switch your device off, but "you can't turn your brain off."

Experts advise people to keep devices out of bed. According to Hartstein, this separation helps your brain associate your bed with sleep rather than whatever you might be watching or reading.

More research is needed

The conflicting science on blue light has led specialists to move away from one-size-fits-all warnings. Hartstein stressed that focusing only on blue light misses the broader picture. "The link between blue light and sleep is murkier than we thought," she said.

Figueiro echoed that even when blue light from screens lowers melatonin, the effect may be too small to matter. "It's still not clear whether the levels of melatonin suppression from screen exposure are enough to impair sleep in the first place," she said.

For Allison Harvey, a professor and clinical psychologist at the University of California, Berkeley, the key message is that evidence remains limited. "We really need more research," she said.

In the meantime, experts recommend paying attention to both habits and personal outcomes. Ultimately, Hartstein said, the real test is whether you wake up feeling restored. "If you are able to fall asleep quickly, you sleep well throughout the night, and you feel rested the next day, then that's great," she said. "You don't need to constantly adjust your behaviors."