Very frequent use of social media does damage the mental health of teenage girls but it causes harm indirectly — through cyberbullying, sleep loss and reduced physical activity — rather than directly by affecting brain development.

That conclusion comes from the first detailed study of how social media affects the mental health of young users, carried out by researchers from Imperial College and University College London and published in The Lancet Child & Adolescent Health journal.

The study examined lifestyle, health, wellbeing and use of technology in a nationally representative cohort of almost 10,000 adolescents in England over three years aged 13-16. During this period frequent users of social media in the sample rose from 43 per cent to 69 per cent of boys and from 51 per cent to 75 per cent of girls.