A large study in Britain found two specific windows of adolescence when some teenagers are most sensitive to social media.
Over the past few years, as the cold glow of a smartphone has followed more and more adolescents from bedroom to school and back again, parents have fretted over the technology’s influence. And no wonder, with Facebook researchers covertly studying how its apps erode girls’ body image, doctors describing TikTok-induced tic disorders, and prosecutors and lawmakers pledging to hold social media companies responsible for harming children.
But in the background, a quieter scientific discussion has questioned whether social media is doing much harm at all. While a few researchers have claimed that digital technology is a powerful, causal factor in the rising rates of mental health problems, others have countered that the risk of harm for most teenagers is tiny — about the equivalent influence on well-being as wearing eyeglasses or regularly eating potatoes, one group calculated.
Now, the authors of the eyeglass paper have published a large, multiyear study providing what independent experts said was an unusually granular and rigorous look at the relationship between social media and adolescents’ feelings about life.
Analyzing survey responses of more than 84,000 people of all ages in Britain, the researchers identified two distinct periods of adolescence when heavy use of social media spurred lower ratings of “life satisfaction”: first around puberty — ages 11 to 13 for girls, and 14 to 15 for boys — and then again for both sexes around age 19.
Like many previous studies, this one found that the relationship between social media and an adolescent’s well-being was fairly weak. Still, it suggested that there were certain periods in development when teenagers may be most sensitive to the technology.
“We actually considered that the links between social media and well-being might be different across different ages — and found that that is indeed the case,” said Amy Orben, an experimental psychologist at Cambridge University, who led the study.
For most adolescents in the United States, screens are a big part of life. Nine out of 10 American teenagers have a smartphone, and they are spending many hours a day staring at it — watching videos, playing games and communicating through social media, recent surveys show.
As social media use among teenagers has exploded over the past two decades, so too have rates of depression, anxiety and suicide, leading scientists to wonder if these striking trends could be related.
Some have suggested that social media may have an indirect effect on happiness by displacing other activities, like in-person interactions, exercise or sleep, that are crucial for mental and physical health. Heavy social-media use seems to disturb adolescent sleep patterns, for example.
Still, research looking for a direct relationship between social media and well-being has not found much.
“There’s been absolutely hundreds of these studies, almost all showing pretty small effects,” said Jeff Hancock, a behavioral psychologist at Stanford University who has conducted a meta-analysis of 226 such studies.
What is notable about the new study, said Dr. Hancock, who was not involved in the work, is its scope. It included two surveys in Britain totaling 84,000 people. One of those surveys followed more than 17,000 adolescents ages 10 to 21 over time, showing how their social media consumption and life-satisfaction ratings changed from one year to the next.
“Just in terms of scale, it’s fantastic,” Dr. Hancock said. The rich age-based analysis, he added, is a major improvement over previous studies, which tended to lump all adolescents together. “The adolescent years are not like some constant period of developmental life — they bring rapid changes,” he said.
The study found that during early adolescence, heavy use of social media predicted lower life-satisfaction ratings one year later. For girls, this sensitive period was between ages 11 and 13, whereas for boys it was 14 and 15. Dr. Orben said that this sex difference could simply be because girls tend to hit puberty earlier than boys do.
“We know that adolescent girls go through a lot of development earlier than boys do,” Dr. Orben said. “There are a lot of things that could be potential drivers, whether they’re social, cognitive or biological.”
Both the boys and girls in the study hit a second period of social media sensitivity around age 19. “That was quite surprising because it was so consistent across the sexes,” Dr. Orben said. Around that age, she said, many people go through major social upheaval — like starting college, working in a new job or living independently for the first time — that might change the way they interact with social media, she said.
Although the new report drew from richer data sets than previous studies did, it nevertheless lacked some information that would be helpful in interpreting the results, experts said. Waiting a whole year between responses is not ideal, for example. And although the surveys asked how much time the participants spent communicating on social media, they did not ask how they used it; talking to strangers while simultaneously playing a video game might lead to different effects than texting with a group of friends from school.
Taken together with past work, the findings suggest that while most teenagers are not affected much by social media, a small subset could be significantly harmed by its effects. But it is impossible to predict the risks for an individual child.
“For your 12-year-old, what does that mean for them? It’s hard to know,” said Michaeline Jensen, a clinical psychologist at the University of North Carolina at Greensboro. Given the small effect seen in the study, “very few of these kids would be going from normal functioning to clinical levels of depression,” she said. But “that’s not to say that none of them would.”
Dr. Jensen pointed out that the study also found a link in the opposite direction: For all ages, participants who felt bad about their lives wound up spending more time on social media a year later. This suggests that for some people the technology may be a coping mechanism rather than the cause of their gloom.
All these experts said that they were often frustrated by the public debates about social media and children, which so often inflate the platforms’ harms and ignore the benefits.
“It carries risks — peer influence, contagion, substance use,” Dr. Jensen said. “But it can also carry lots of positive things,” like support, connection, creativity and skill mastery, she added. “I think a lot of times that does get overlooked because we’re so focused on risks.”