Study finds first smartphone at age 13 not linked to poorer mental health, but heavy use harms teens

A year‑long study of 1,959 U.S. adolescents, led by Ran Barzilay at the University of Pennsylvania and published in JAMA, examined the impact of receiving a first smartphone at age 13. The researchers found that simply acquiring a phone at that age was not significantly associated with depression or obesity, but it was linked to insufficient sleep (less than eight hours) at age 14. Moreover, adolescents who used their phones for more than five hours per day showed higher rates of depression, obesity and sleep deficits compared with those who limited use to under two hours daily. Barzilay emphasized that “the acquisition of the first smartphone at 13 does not itself worsen mental health,” but that “duration of use and nighttime access are crucial.” The study recommends limiting screen time and keeping phones out of bedrooms at night to protect teen health. These findings contrast with earlier research by the same team that associated first phone use at age 12 with poorer mental health.