A Swedish study involving 4,810 students aged 12 to 16 found that teenage girls who spend more time on their phones are more likely to experience poor sleep and higher depression scores compared to boys. The research indicates that excessive screen time leads to sleep displacement and impacts sleep quality. While the findings suggest a correlation between high screen time and depression, further research is needed to establish causation. Experts recommend national guidelines on smartphone use to help improve adolescents' sleep.