It's something we might feel we know intuitively: excessive smartphone scrolling is bad for mental health, especially among developing teenagers. 

Each year, we hear new reports of youth mental health crises. We may even notice the effects of excessive phone use in our own lives. Kids, too, are spending more time on their phones than ever before, that's something anyone who spends time with teenagers can see.

As it turns out, the link between mental health and the overuse of mobile technology is harder to prove than you might think.  

What screen time does to teenagers

A new study conducted in South Korea attempts to measure this link using self-reported screen time, a methodology that, despite being very common in this line of research, has come under criticism from tech researchers in recent years.

The study, published in the journal PLOS ONE on December 6, looked to examine what increased screen time means for teenagers' mental health.

It isn't a new topic, researchers have been trying for years to quantify the degree to which mobile technology — and social media in particular — is bad for youngsters. However, it marks the first time researchers have tried to track any potential relationship on a national scale.

The researchers used two surveys conducted among South Korean youths in 2017 and 2020 respectively, asking over 40,000 teenagers how many hours per day they spent on their phones on average. Teens were also asked about mental health, substance use and obesity.

As expected, they found screen time increased significantly between 2017 and 2020, from 30% reporting screen times of over 4 hours per day in 2017, to over 55% in 2020. They also found that all three categories tested — negative mental health outcomes, substance abuse, and obesity — increased the more time children spent on their phones.

The study's results are consistent with what we already know about the subject. The corelation between an increased use of mobile technology and diminished mental health is uncontestable. But the paper's shortcomings — outlined by the researchers themselves — are significant.

"The reported usage time may not be an estimate of the actual usage time and could be underestimated due to the tendency to provide socially desirable and acceptable answers," they wrote.

Additionally, researchers didn't track what exactly these youngsters were doing on their phones in the first place. Were they looking at TikTok? Having long video calls with friends? Playing games?

They addressed this too: "We could not specify the smartphone usage time according to the purpose (e.g., social media use, text messaging, education, online shopping), which could have affected the health outcomes," they wrote.

'Meaningless'

Peter Etchells, a professor of psychology and science communication at Bath Spa University in the UK, said that measuring screen time as a concept is "pretty meaningless."

"It covers literally anything and everything, and for many years now, researchers have been calling for a more nuanced approach that more fully considers the specific content and context of use," he told DW in an email.

Being a simple number, screen time is easy to measure in research papers, he said.

"But if you imagine two people reporting three hours of screen time per day, those three hours can cover such a varied range of activities, it's nonsensical to try and correlate that simple number with something else, like well-being," he said.

Etchells, who is working on a book on the science of screen time next year, said the question researchers should be asking isn't what the relationship between increased screen time and mental health may be, but rather: "Why is it the case that some people encounter difficulties when they use digital technology, and other people appear to thrive?"

He is basically saying that when it comes to measuring the impact phones have on mental health, the important metric to use isn't time spent using the technology, but rather what we are doing when we are using it — and how those activities may or may not impact mental health.

Edited by: Sushmitha Ramakrishnan