A study by the team of adolescent psychiatrist Ran Barzilay at the Children’s Hospital of Philadelphia, cited by BlockTempo on June 9, shows that for children who get their first smartphone at age 13, there is "no association" between depression and obesity. The study also found that teenagers who use smartphones for more than 5 hours per day have more than double the risk of developing depression, obesity, and insufficient sleep within one year after getting a phone.
Research Design and Data
Ran Barzilay’s team published a new study analysis in JAMA Pediatrics of 1,959 teenagers: 1,230 received their first smartphone between ages 13 and 14, while 729 had no smartphone; after one year of follow-up, health outcomes were tracked.
An earlier lead study published in Pediatrics used data from the US Adolescent Brain Cognitive Development (ABCD) database, analyzing longitudinal data across 21 research sites, involving more than 10,588 teenagers, covering five assessments from 2016 to 2022, and confirmed a significant association between getting a phone at age 12 and depression, obesity, and insufficient sleep. Barzilay explained that controlling usage time and usage location is “a very direct intervention or behavioral adjustment that can bring about a lot of change.”
Phone and Social Media Restriction Policies for Teenagers in Different Countries
Australia: Starting December 10, 2025, it will ban users under 16 from having social media accounts; noncompliant platforms may be fined up to about 50 million Australian dollars; as of mid-December, about 4.7 million underage accounts have been removed.
France: Bans social media use for those under 15 (parents may consent for use starting at age 13).
Denmark: Drafting a ban for those under 15.
Portugal: Restricts for those under 16.
Malaysia: Plans to ban those under 16, with formal implementation planned for 2026.
FAQ
Why is 13 considered a relatively safe starting age for a phone?
According to the study published by Barzilay in JAMA Pediatrics, children who get their first smartphone at age 13 have “no association” with depression and obesity after one year of follow-up; children who already have a phone at age 12 show a significantly higher risk. Barzilay told the media that 13 is a “relatively safe starting point,” but emphasized that time-of-use controls are still necessary.
What are the specific risks for using smartphones more than 5 hours per day?
Based on the study data, teenagers who use smartphones for more than 5 hours per day have more than double the risk of developing depression, obesity, and insufficient sleep within one year after getting a phone. The study found that simply moving the phone out of the bedroom can significantly reduce the risk of insufficient sleep.
How effective is Australia’s social media ban for those under 16 currently?
Australia’s regulations are enforced by eSafety Commissioner Julie Inman Grant, and noncompliant platforms may be fined up to about 50 million Australian dollars. As of mid-December 2025, about 4.7 million underage accounts have been removed.
