Almost everyone knows the moment: you pick up the phone for one thing and put it down forty minutes later, not quite sure where the time went. Researchers from the University of Cincinnati and Northwestern University went looking for the point at which that habit stops being ordinary. They pooled eleven surveys gathered between 2014 and 2024, covering some 183 000 American adults, and landed on a threshold of around 150 minutes a day – and at the end you can look at how your own day with a phone is actually built.
Nobody plans to spend an evening scrolling. It simply happens: a quick look at one app turns into a second one, and the phone goes down much later than intended. The question that follows is always the same – is that a lot, or is that already too much? Until recently there was no number to hang an answer on, only a vague feeling that something had drifted.
A team from the University of Cincinnati and Northwestern University set out to attach a figure to it. What they found is not a verdict on anybody, but it is a point of reference, and that on its own is rare in this discussion.
The researchers did not run a new experiment. They went back to eleven surveys carried out between 2014 and 2024 and pooled the answers of roughly 183 000 American adults aged 18 to 70. Participants had answered yes-or-no questions about 31 health conditions, alongside questions about how they spent their time in front of a screen.
The scale is the whole point. In a sample of a few hundred people a weak association vanishes into noise; in a sample this size, statistical models can separate it from age, income or lifestyle. The results appeared in Mental Health Research, a journal in the Nature Portfolio series.
The analysis covered several different ways of spending time in front of a display:
Only the first of them stood out. Social media turned out to be a considerably stronger predictor of the severity of depressive symptoms than television, gaming or email – worth remembering the next time screen time gets treated as one undivided block of hours.
The threshold the authors point to sits at around 150 minutes of social media a day: two and a half hours. Below it the association is weak enough to be easy to overlook. Above it, it shows up clearly in the data.
“When it comes to depression and social media, the argument is salient across scientific test after test of those 11 years,” commented Hans Breiter of the University of Cincinnati, the corresponding author of the paper.
It is worth being precise about what that threshold is. It is not a safe daily allowance, and crossing it is not an event that happens to a person. It is the point at which a pattern becomes visible in a very large set of answers.
Part of the explanation the authors reach for lies in how the services changed over the decade the surveys cover. “Initially, social media was a social outlet with people you knew,” said Nicole Vike, a senior research associate at the University of Cincinnati and a co-author of the study. Today a feed is filled mostly with material from strangers, assembled to keep a viewer in place.
Breiter sets the contrast plainly: “Mental health and happiness are about engaging the world and having purpose, not passively watching something for hours.”
This is the part most easily lost on the way to a headline. The work shows a correlation, not a cause. It does not establish that social media produces depression, and the authors do not claim that it does; the relationship could run the other way round, or both could follow from something else entirely.
What the team offers is a starting point for further research and a number that can be tested – not a diagnosis, and not advice.
Beyond its subject matter, the paper is a compact lesson in how social research on very large samples works. Eleven surveys, a decade and 183 000 respondents buy statistical power – but every answer is still a self-report, given once, at a single moment.
That shapes what can be concluded. A survey can show that two things occur together and estimate how strongly; it cannot show which of them came first. Martin Block, professor emeritus at Northwestern University and a co-lead author, puts the scale of the phenomenon in perspective: “Social media is a common marker of our cultural age much like the automobile was more than a century ago.”
Eleven surveys, ten years, 183 000 adults and one number: about 150 minutes a day, past which the link between social media and the severity of depressive symptoms becomes clearly visible in the data. Television, games and email did not behave the same way. The finding is a correlation, and the researchers say so themselves – which makes the screen time counter sitting in every phone a piece of data worth a glance rather than a reason for a verdict.
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