Tired of battling with teenage children about putting their mobile phones away before bed?
Take heart. Scientists say parents are right to be worried about the effects of chatting with friends on social media before going to sleep.
A study has found teenagers who use websites such as Facebook within 30 minutes of bedtime tend to perform worse than their peers in class.
The researchers, from University College London, said this may be because it over-stimulates the brain, making it difficult to sleep afterwards. Teenagers are then less likely to get the recommended 10 hours of sleep they need to function well at school the next day.
In a survey of 16 to 19-year-olds, 70 per cent said they use social media before bed - and they achieved, on average, exam grades 20 per cent worse than those who did not.
