As Chapter 2 describes, the prevalence of mental health conditions among adolescents is unacceptably high. Up to 50% of all mental health conditions start before the age of 14 years, and as many as one in every five adolescents experiences a mental disorder each year. Suicide is one of the leading causes of death among older adolescents. Poor adolescent mental health is associated with a range of high-risk behaviours, including self-harm; tobacco, alcohol and substance use; risky sexual behaviours; and exposure to violence, the serious effects of which persist throughout life. The COVID-19 pandemic severely reduced the well-being of young people and put them at increased risk of suicide, substance use and other mental health problems. Additionally, adolescents living in challenging situations, such as protracted conflicts, may need more mental health attention.