'There's more to life than staring at a small screen': a mixed methods cohort study of problematic smartphone use and the relationship to anxiety, depression and sleep in students aged 13-16 years old in the UK.

Background: Depression and anxiety are common in adolescents and have increased over the last decade. During that period, smartphone usage has become ubiquitous.

Objectives: The study aim was to assess the association between problematic smartphone usage (PSU) and anxiety.