New Study Links Smartphones at Age 12 to Depression, Obesity and Insufficient Sleep

Smartphones and health at age 12

As understanding grows of how smartphones shape childhood, a new study of young people approaching adolescence offers further unsettling evidence.

US researchers found that having a phone at 12 was linked with a higher likelihood of depression, obesity and inadequate sleep than not owning one.

The iPhone launched less than 20 years ago, meaning many children now moving into their teenage years have never experienced a world without phones. Research such as this is attempting to separate out their effects.

"Our findings suggest that we should view smartphones as a significant factor in teen health, approaching the decision to give a child a phone with care and considering potential impacts on their life and health," says child and adolescent psychiatrist Ran Barzilay, from the Children's Hospital of Philadelphia.

What the adolescent brain development data showed

The analysis drew on data from 10,588 young people taking part in an ongoing adolescent brain development study. It offered a picture of their health at 12, alongside some indication of the difference acquiring a phone - or not doing so - could make during the following year.

After accounting for factors including demographics and socioeconomic status, the team found that nearly 6.5 percent of 12-year-olds with phones had received a depression diagnosis, compared with roughly 4.5 percent of those without a phone. Although apparently modest, this was a meaningful statistical gap.

Obesity affected roughly 18 percent of smartphone users, versus 12 percent of 12-year-olds who did not have these devices.

In terms of sleep, 47 percent of 12-year-olds who owned phones said they were not getting enough sleep - less than nine hours each night - compared with 31 percent of peers without phones.

Those who had obtained a phone by 13 were more likely to report mental health difficulties, including depression, and insufficient sleep than those who had not. Over that year, however, no discernible difference emerged in obesity risk.

Potential benefits and limits of the study

The researchers acknowledge that phones can be beneficial, as previous studies have indicated, but argue that more should be done to ensure these devices are used responsibly.

"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," says Barzilay.

"Likewise, some families may view a smartphone as a necessity for safety or communication."

The data also have important subtleties. Depression, for instance, was recorded as any episode during the child's life up to that point, meaning it could in some cases have happened before they received a phone.

Because this was an observational study, it cannot establish cause and effect. Still, the strength of the links - together with the changes observed between ages 12 and 13 as some children gained phones while others did not - merits further examination.

The results align with evidence on adults and smartphones: these devices may increase stress, make people feel more distracted and exhausted, and alter how the brain is wired.

Future work will examine how screen time levels and different kinds of apps influence these outcomes, whether the findings continue across longer stages of adolescence, and which countermeasures might help.

"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," says Barzilay.

The research has been published in Pediatrics.