This briefing provides data on the prevalence of mental disorders among adolescents, aged 11–19 years, in England, including data gathered during the Covid-19 national lockdown.

• More than one in seven young people (15.3%) aged 11–19 in England had at least one mental disorder in 2017. 
• A follow-up survey carried out during the Covid-19 lockdown (July 2020) indicates that one in six young people (17.6%) aged 11–16 years were identified as having a probable mental disorder. This figure increases to one in five (20.0%) among young adults aged 17–22. 
• Emotional disorders such as anxiety and depression are the most common mental disorders experienced by young people.
• The rate of mental disorders among 11–15-year-olds in England seems to be increasing, having risen from 11.4% in 1999 to 13.6% in 2017. The latest data from 2020 suggest that young people’s mental health has further deteriorated.
• In younger adolescents (aged 11–16), the prevalence of mental disorders is similar among boys and girls. However, among older adolescents (17–19), mental disorders are more common in girls, with almost one in four girls (23.9%) experiencing a mental disorder, compared with one in 10 boys (10.3%).
• Self-harm and attempted suicide are around six times more common among adolescents (aged 11–19) with a mental disorder (32.8%) than those without (5.1%). Similar to mental disorders, rates of self-harm and attempted suicide among the adolescent population are increasing, with reported self-harm having increased from 5.3% in 2000 to 13.7% in 2014 (11–16-year-olds).
• While these increases over the last two decades may reflect more accurate reporting – potentially due to increased awareness and help-seeking behaviours, reduced stigma and improved screening – they may also represent an increase in prevalence rates. Further research is required to understand these trends. 
• The increasing concern around young people’s mental health, particularly in relation to the Covid-19 pandemic, highlight the need for immediate action to support young people most at risk. It is essential that this action is underpinned by a strong evidence base.
• Early intervention, including promotion and prevention strategies, has the potential to produce the greatest impact on young people’s mental health and wellbeing by taking action before mental health problems worsen and preventing the onset of mental disorders.

The majority of data in this evidence brief is based on the Mental Health of Children and Young People (MHCYP) survey, from four waves: 2020, 2017, 2004 and 1999. Data on suicide and self-harm is drawn predominantly from the 2017 MHCYP survey (NHS Digital, 2018), alongside the 2014 Adult Psychiatric Morbidity Survey (APMS), which reports on self-harm and attempted suicide among 16–24-year-olds in the UK, and ONS data on the number of completed suicides in 2019 in the UK.