Over the years, the advice from scientists and experts to people of all ages has been pretty universal: Using your phone before bed will help. ruin your sleep.
But the conclusions obtained new research conducted by Toronto Metropolitan University (TMU) and Laval University paint a more complex picture modern night habit.
The study asked more than 1,000 adults across Canada about their screen use before bed and sleep health. They found that overall sleep status was similar between those who used screens every night and those who didn't use them at all. The worst sleepers were those who only used their phone a few nights a week.
While previous studies have blamed sleep disruption on blue light emitted by phones and other LED screens, which some studies say limits the body's production of the sleep hormone melatonin, the TMU researchers said these findings did not take into account age, timing or intensity of exposure.
Read more: 20 things you shouldn't do before bed
TMU Professor Colleen Carney, One of the study's authors, an expert in sleep and mood disorders, said other studies in the field have used experimental conditions that don't reflect the average person's day, and in some cases “stack the deck” to prove blue light is to blame.
“It's true that we have these studies, but in order to get these results, these studies typically select young people who are closer to puberty, which is really important because it makes you sensitive to light. And then they are kept in a laboratory overnight and all day long, they are in dim light all day long,” Carney told TIME. “I think people have taken the results in this area and applied them too broadly and haven't paid attention to the studies that didn't find them.”
Carney says research has shown that it's just as important that people do on your phone, especially “if you're doing things that are really hard to tear yourself away from, if you're doing things that are frustrating or annoying to your phone.”
Studying, published in magazine Sleep health in October, ughand that more than 80% of participants reported using screens before bed in the past month, and nearly half reported using screens every night.
Carney's research follows some similar findings in recent years that suggest blue light may have been unfairly maligned.
Research over the years has pointed in one direction: Blue light can disrupt sleep and potentially delay the release of melatonin, so limiting it is the best way to get a good night's sleep.
Several studies have shown that exposure to short-wave blue light reduces melatonin levels, thereby negatively affecting sleep.
A 2011 study published in Journal of Applied Physiology found a link between blue light exposure and melatonin suppression. Another 2023 study published in Brain Communications measured sleep in teenage boys and young adult men after reading using a regular book or a blue-light-emitting phone. The results supported the idea that melatonin can be suppressed by blue light, but also found that the negative effects could be mitigated by putting your phone away at least an hour before bed. A study published in April 2025 in the journal Life highlighted that blue light disrupts circadian rhythm and found that red light was a better alternative.
Other studies have found a strong link between phone use and poor sleep quality, but have been unable to determine causation.
A 2016 study published in the journal PLOS ONE and published in TIME magazine found a strong link between phone use before bed and poor sleep, without drawing any conclusions about cause and effect. The 30-day study measured screen time in 653 adult participants in the United States.
“We can't rule out the possibility that people who simply can't fall asleep for some unrelated reason are filling that time by using their smartphone,” study co-author Dr. Gregory Marcus said. told TIME in 2016.
The National Sleep Foundation's 2024 Expert Panel, consisting of 16 sleep and pediatric experts, published a consensus statement saying that screen use in general worsens sleep health in children and teens, but primarily because of the content. The expert panel did not reach a consensus on whether exposure to blue light from screens before bed could impair sleep in adults.
A American Cancer Society Study, March 2025 More than 122,000 participants found that daily screen use was associated with later bedtime and about 50 minutes less sleep per week.
Dr. Alex Dimitriou, a psychiatrist and sleep medicine physician in Menlo Park, California, calls the study “fascinating because it contradicts a very large body of established research that suggests a clear impact of screen use on sleep quality,” citing the American Cancer Society's 2025 study as an example.
“The authors acknowledge some interesting findings [including] this cause-and-effect relationship cannot be clearly determined based on this study. And it’s quite possible that good sleepers either use their phones or not, and bad sleepers don’t know what to do,” Dmitry told TIME.
In Dmitry’s professional opinion: “Screens are bad for sleep.”
“I can't sleep [for] spending hours scrolling through news articles, blogs, and social media posts. If I try to read a book, I'll be out of the game within 10 minutes. My patients feel the same way,” he says. “The screens, in addition to being bright, are also too interesting.”
The TMU study is not the first of its kind to suggest that blue light may not be a major contributor to sleep disruption.
Several other studies also show that research on blue light and sleep is mixed. 2022 review in Frontiers in Psychology looked at 24 studies to answer this exact question among young people. One in five studies reported worse sleep quality after exposure to blue light, and one in three reported decreased sleep duration. Fifty percent of studies showed a reduction in fatigue, consistent with increased blue light activity and improved daytime cognitive function.
“[I]Overall, the specific effects of blue light exposure still remain an unclear area, and more research is needed before definitive evidence-based conclusions can be drawn,” the study says, although the researchers say blue light “may also have negative effects, such as decreased sleep quality and duration, which can impair an athlete’s physical and cognitive performance and recovery.”
The TMU researchers note that young people may be more vulnerable to light exposure that suppresses melatonin production, and many studies have shown that nighttime light exposure may particularly affect children and adolescents, rather than the adults on whom the TMU study focused.
“There may be reason to be cautious about overexposure to blue light in the evening among adolescents because puberty increases sensitivity to light,” Carney said in a newspaper press release. “As we age, we are less sensitive to light, and there are age-related effects on the eyes that make light less damaging.”
