Pediatric Neurologist Reveals How Much Smartphone Time Leads to Health Risk

Adolescents who use smartphones for more than 4 hours per day may be at higher risk of adverse mental health outcomes, a study has suggested.

The research, published in the journal PLOS ONE, analyzed data on more than 50,000 South Korean adolescents taking part in an ongoing survey.

The research found that smartphone usage for more than 4 hours a day was associated with higher rates of stress, suicidal thoughts and substance use compared to usage of below 4 hours per day.

It is important to note that the study does not confirm a causal relationship between smartphone use and adverse health outcomes. Nevertheless, the findings could help to inform usage guidelines for adolescents, the authors said.

Smartphones have become widespread among among young people and evidence suggests that their use has increased significantly in recent years. But a growing body of evidence has shown that this usage is associated with a higher risk of many adverse health effects in adolescents—including sleep difficulties, eye-related problems, psychiatric disorders and even musculoskeletal issues.

Recent research has also found that at least some daily internet usage may be associated with better physical and mental health outcomes in adolescents.

To examine the relationship between adolescent smartphone use and health, a team of South Korean researchers analyzed survey data collected between 2017 and 2020. This data included the approximate number of daily hours each participant spent on a smartphone as well as a variety of other health measures.

The analysis took into account other factors that could be linked to health outcomes, such as age, sex and socioeconomic status.

The researchers found that the proportion of adolescents in the study who used a smartphone for more than 2 hours a day in 2020 was more than 85 percent—up from around 64 percent in 2017.

The study revealed that adverse health outcomes were prominent in those who used a smartphone for more than 4 hours per day. However, adolescents using smartphones 2–4 hours per day showed no increased adverse health outcomes compared to non-users, except for smartphone overdependence. Finally, adolescents that used a smartphone only for 1-2 hours a day actually appeared to encounter fewer problems than those who did not use one at all.

"This implies that appropriate smartphone usage can be prosocial and enjoying smartphone use should not be conceptualized as a behavioral addiction such as gambling and playing video games," the authors wrote in the study. "Children and teenagers spend considerable time using smart devices as a social platform for peer relationships."

"Using a smartphone for 4 hours a day seems to be generally acceptable. From our results, using smartphones for less than 2 hours a day even seems beneficial for mental health outcomes compared to non-use."

Given that a causal relationship has not been demonstrated, the authors said caution must be taken in interpreting the results of the study, which do not imply that using a smartphone for more than 4 hours a day is always undesirable. Nevertheless, the results suggest that smartphone usage beyond certain levels could "significantly" affect health outcomes.

In addition, the study has other limitations. For example, it relied on individuals' self-answered questionnaires on smartphone usage time and health outcomes, which may not be completely reliable. Furthermore, the researchers could not specify the smartphone usage time according to the purpose—for example, social media use, education, online shopping—which could have affected the health outcomes.

Overall, the researchers said the study will provide useful information for establishing smartphone usage guidelines for adolescents and young adults.

Kevin Koban, a postdoctoral researcher in the Department of Communication at the University of Vienna in Austria, who was not involved in the paper, told Newsweek the study is "well-conducted" and its results closely correspond to recent findings on the effect of smartphones, and media in general.

"The study certainly has its limitations, most notably concerning its cross-sectional survey design and reliance on self-report measurements, which does not allow for causal interpretations and makes it vulnerable to answering biases, respectively," he said.

This "should be taken very seriously when interpreting the findings. However, this doesn't mean the study is inherently flawed or shouldn't be considered," he said.

Some research has previously suggested that moderate levels of digital media use among young people appears to be just right for balancing out the potentially beneficial and harmful consequences of use.

"This so-coined Goldilocks Hypothesis is supported here again in a different setting, indicating that it may indeed be valid, which challenges some accepted assumptions about what healthy smartphone use may look like," Koban said.

The main implication of the study, according to Koban, is that even when one disregards how exactly smartphones are used and only focuses on the overall frequency, there seems to be an optimal level of smartphone engagement that is moderate in length.

"This creates obvious challenges for some publicly prevalent positions, like perhaps outdated and overly cautious screen time limits or other restrictive parental mediation ideals," he said. "Instead, it points toward the necessity of a more nuanced view to find the optimal balance across media, contexts, and individuals."

The results from South Korea might not necessarily be applicable to other adolescent populations. But comparable findings from other industrialized regions suggest that the similarities between different populations might outweigh the contextual differences, according to Koban.

With regards to potential causal mechanisms, Koban said different ones might be relevant depending on the direction of any given effect—that is, whether excessive smartphone use causes adverse mental health outcomes, or problematic mental health conditions cause excessive smartphone use.

"For example, excessive smartphone use could result in other, perhaps more beneficial activities being somewhat neglected or[...]exposure to stress-inducing information," he said. "The other way around, mental health issues may possibly come with an over-reliance on smartphone use as a coping tool.

"Generally, it is improbable that there is a single causal factor here; instead, it is much more likely that we talk about an individually variable combination of several underlying mechanisms that might be responsible in either way."

Update 12/21/23, 7:50 a.m. ET: This story was updated with comments from Kevin Koban.