Excerpt from this article (thanks Daan for the link!):
The research suggests that the most critical stage for tackling the problem of digital addiction and school burnout is age 13-15. The most effective way of supporting adolescents’ mental health and preventing excessive internet use is to promote school engagement, to build up students’ motivation to learn, and to prevent school burnout.
Depressive symptoms and school burnout in late adolescence are more common among girls than boys. Boys suffer more from excessive Internet use than girls.