A study suggests using social media isn't directly harming teenagers, but it can reduce the time they spend on healthy activities, such as sleeping and exercising.
Parents should ban phones from bedrooms after 22:00 and encourage more physical activity, BBC news reported, citing UK researchers.
51% of the girls and 43% of the boys used social media more than three times a day, rising to 69% of boys and 75% of girls by Year 11.
The study found that girls were particularly vulnerable to cyber-bullying on social media, which could lead to psychological distress.
In the UK, nine out of 10 teenagers use social media and there is growing concern about its impact on the mental health and the wellbeing of young people.