A South Korean study found Thursday that teenagers who use smartphones for more than four hours a day are at higher risk of mental health problems. Researchers at Hanyang University Medical Center analyzed data from 54,809 teenagers across the country to find correlations between the time spent using smartphones each day and adverse outcomes such as stress, depression, suicide, drug use and smartphone overdependence. They used data from the 2017 and 2020 Korean Youth Risk Behavior Online Surveys conducted by the state.
It was found that the curvilinear relationship between smartphone use time and adverse health outcomes was evident after four hours of daily use. While teens who used smartphones for 2 to 4 hours a day showed signs of overdependence on their smartphones, they did not show more adverse health consequences than teens who did not use smartphones.
"Smartphone use for less than four hours per day was significantly associated with feelings of stress, suicidal idealization, and substance use after propensity score matching," the researchers wrote in the study. "This study used propensity score matching to help account for other factors that may be associated with outcome, gender, age, and socioeconomic factors."
Compared with the four hours or less group, the four or more hours group had a 16% higher tendency to perceive stress, 17% higher sleep dissatisfaction, 22% higher depressive symptoms, 22% higher suicidal thoughts, 17% higher suicide plans, 20% higher suicide attempts, 66% higher alcohol problems, and 90% higher smoking. They are more than twice as likely to be overly dependent on their smartphones and 9% more likely to be obese.
However, teens who use smartphones for one to two hours a day are actually less likely to experience adverse health effects than teens who don't use smartphones at all.
The survey found that compared with 2017, the prevalence of smartphone use among teenagers has increased in 2020. 85.7% of teenagers use smartphones for more than two hours a day in 2020, compared with 64.3% in 2017. The proportion of people using smartphones for less than two hours was 35.7% in 2017, but plummeted to 14.4% in 2020.
"Our study demonstrates a curvilinear relationship between the amount of time adolescents use smartphones and adverse health outcomes. Our findings could help develop guidelines for smartphone use among adolescents," the researchers wrote.
The research was published in the open access journal PLOSOne.