The earlier that adolescents are given smartphones, the more likely they are to develop depression, gain weight and not get enough sleep, researchers from the Children's Hospital of Philadelphia and Penn Medicine found.
About 95% of U.S. teens 13 to 17 either own or have regular access to smartphones, and nearly 60% of children 11 to 12 have them, the Pew Research Center found in a recent survey. The percentage of teens who say they use the internet "almost constantly" nearly doubled from 24% in 2014-15 to 46% by 2023.
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Researchers at CHOP and Penn Medicine sought to understand how kids' health changes when they get smartphones and whether their age influences the effects of using the devices. They analyzed data from more than 10,000 teens in the U.S. between 2018 and 2022, adjusting for a range of factors including socioeconomic status, ownership of other electronic devices and parental monitoring of phone use.
Among the adolescents in the study, nearly two-thirds had a smartphone by the time they were 12.
"Owning a smartphone by age 12 is associated with worse health outcomes across the board — more depression, more obesity, more insufficient sleep," Ran Barzilay, a CHOP psychiatrist and one of the study's lead researchers, said in a presentation of the findings.
The risk of obesity and insufficient sleep increased the younger kids were when they got a smartphone, the study found, and these issues began within a year of smartphone ownership. Among kids who did not have a smartphone when they turned 12, getting one within the following year was associated with a greater risk of mental health problems and poor sleep at 13 compared to those still didn't own a smartphone at that age.
The study, published Monday in the journal Pediatrics, notes that nearly all teens will have smartphones to stay connected with family and friends. Though previous studies have found a correlation between negative health outcomes and screen time, little research has focused specifically on smartphones.
"We're not claiming smartphones are detrimental to all adolescents' health," Barzilay said. "Rather, we advocate for thoughtful consideration of the health implications, balancing both positive and negative consequences. For many teens, smartphones can play a constructive role by strengthening social connections, supporting learning, and providing access to information and resources that promote personal growth."
The study, which included contributions from researchers at the University of California, Berkeley and Columbia University in New York, comes amid rising concerns about how digital technology impacts kids' mental and physical well-being.
About 71% of the parents surveyed by Pew in 2020 said they believe widespread use of smartphones by young children might result in more harm than benefits. When asked when it's appropriate for kids to have smartphones, 73% said only after kids turn 12. About 45% said 12 to 14, 28% said 15 to 17, and 22% said it's OK for kids under 12 to have them.
Parents had more permissive views about tablets, including about 65% who said it was acceptable for kids to have their own before turning 12. But about 86% of parents said they limit screen time, and 80% said they take away privileges as a punishment. Another 75% said they check the apps and websites their kids use.
Last year, then-U.S. Surgeon General Vivek Murthy called for social media companies to be required to provide warning labels that advise parents and their kids about the mental health risks of using their platforms. Minnesota and California have passed laws that will require such labels in the coming years, and New York could become the third state to mandate them. California's law will require apps like Instagram, Snapchat and TikTok to display 30-second warnings whenever users under 18 spend more than three hours on their sites, with additional warnings shown every hour after that.
To prevent excessive screen time, the CHOP researchers advised parents to monitor how their kids use smartphones and to set clear rules about when and where they can use them. The researchers also recommended parents take advantage of privacy and content settings to protect their kids and regularly discuss issues related to phone use and health.
"It's critical for young people to have time away from their phones to engage in physical activity, which can protect against obesity and enhance mental health over time," Barsilay said.