As with young children, there are reasons for concern over large amounts of screen time in tweens and teens. Correlational studies have shown that 8- to 11-year-olds who exceed screen time recommendations scored lower on cognitive assessments, with compliance with recommendations explaining about a fifth of the overall variance in cognitive scores (
The Lancet Child & Adolescent Health, Vol. 2, No. 11, 2018). A combination of screen time and too little sleep has also been associated with heightened impulsivity in the same age group (
Pediatrics, Vol. 144, No. 3, 2019).
These studies weren’t designed to show causal relationships, though, says Gary Goldfield, PhD, a psychologist at the University of Ottawa who coauthored both studies. It could be that increased impulsivity or struggles with cognition drive the excess screen time. Nevertheless, in numerous studies, Goldfield and his team have consistently found the best mental health and cognitive outcomes in teens who do one hour of physical activity each day, sleep eight to 10 hours a day and use screens recreationally less than two hours a day.
Researchers have also found links between screen time and various health outcomes in teens, though again, establishing definitive causal relationships is difficult. The firmest associations are between screen time and obesity and screen time and depressive symptoms, according to a systematic review of reviews published by University College London (UCL) psychologist Neza Stiglic, PhD, and Russell Viner, PhD, a professor of adolescent health at UCL (
BMJ Open, Vol. 9, No. 1, 2019). Most research on obesity focused on television viewing and found that more time spent watching TV was associated with a higher body mass index or body fat composition. Multiple studies also found that screen use of more than two hours a day was correlated with depressive symptoms. The reviewers found moderate evidence linking screen time to poorer quality of life, higher caloric intake and less-healthy diets.