The news is filled with alarming-sounding stories about smartphone use—but what does the evidence actually say? As Brian Resnick reports for Vox, there's reason to believe smartphones could present real hazards—but also that the risks might not be as bad as you think.

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Why the literature on smartphone use is 'a wreck'

A number of high-profile studies have examined the relationship between smartphones and mental health, and some have produced results that seem alarming at first glance, Resnick writes.

For example, a 2017 study led by Jean Twenge—a psychology professor at San Diego State University— found that adolescents who spent more time on social media and electronics were more likely to show symptoms of depression and suicide-related outcomes. Resnick notes that Twenge later wrote a "provocative and widely read" cover story in The Atlantic about his findings entitled "Have Smartphones Destroyed a Generation?"

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But while Twenge's study certainly turned up some notable correlations, Resnick writes, it wasn't designed to prove that smartphones actually caused the negative outcomes. Further, it used fairly broad definitions. For example, the study didn't define "depressive symptoms" as meaning that an adolescent had received a medical diagnosis of depression. Rather, it included respondents who agreed with statements such as, "Life often seems meaningless."

Many other studies on smartphone use share these and other weaknesses. For instance, many rely on participants to self-report their "screen time"—and people are notoriously bad at remembering how much time they've spent using their devices, Resnick writes. A study published in 2016 found that only about one-third people can accurately report much time they spend on the internet.

Further, the whole idea of "screen time" may be of limited value. As Andrew Przybylski, an experimental psychologist at the Oxford Internet Institute, pointed out, in nutrition research "you wouldn't talk about 'food time.' You talk about calories, talk about carbohydrates, fats, and proteins—the idea of 'screen time' contains none of that richness." It blurs together, for instance, time spent on gaming with hours spent on social media, schoolwork, or web browsing.

Yet another challenge is the sheer pace of technological change, which means that "screen time" means something very different in 2019 than it meant a decade ago.

According to Anthony Wagner, chair of the department of psychology at Stanford University, as a result of all of these obstacles, "[t]he literature [on smartphone use] a wreck. Is there anything that tells us there's a causal link? That our media use behavior is actually altering our cognition and underlying neurological function or neurobiological processes? The answer is we have no idea."

So what can we say about the risks of 'screen time'?

Given all these limitations, it's difficult to say for sure whether a causal link exists between smartphone use and mental health. But it's worth bearing in mind, Resnick writes, that even the correlations identified in most studies are relatively low—meaning that the risk, if it exists, could be small.

For example, the Twenge study reported only a .05 correlation between social media use and depressive symptoms—and only a .01 correlation for male adolescents. Its link between device use and "suicide-related outcomes" (a term that includes a range of suicide risk factors) was only .12.

That's "a pretty small positive correlation," Resnick writes, and may have only a limited real-world effect compared to other variables that can affect a child's well-being, such as socioeconomic status.

In a separate study published in Nature Human Behavior, Amy Orben, a psychologist at the Oxford Internet Institute, and Przybylski found a small, negative correlation between digital technology and overall well-being among 355,258 participants. But they also found that wearing glasses had a stronger negative correlation to overall well-being—perhaps because children who wore glasses faced teasing.

Even more strikingly, their study found "the association of well-being with regularly eating potatoes was nearly as negative as the association with technology use." As Resnick notes, "[T]here's no public moral outrage about potatoes, and this is not evidence that kids shouldn't eat them."

As such, the study authors wrote, their data "simultaneously [suggest] that the effects of technology might be statistically significant but so minimal that they hold little practical value."

What's next for smartphone research?

Given the sheer complexity of the question, researchers doubt whether we'll ever have any firm conclusion as to whether screen time is "good" or "bad," or how much is "too much" for any particular child.

Rather, we'll face "endless and complicated" questions, Resnick writes, such as, "Do disadvantaged kids suffer more or fewer consequences from media use? Is media use a problem, or is multitasking the issue? In what cases are the social connections made on apps beneficial?"

These questions are difficult, but we'll ultimately have to tackle them, Orben argued—because if we don't, "we're just going to have this debate without any evidence involved" (Resnick, Vox, 2/20).

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