Young people’s mental health is getting worse, with rising rates of depression, anxiety, psychological distress and poor well-being. Drawing on international data, recent scientific literature and insights from clinical and policy experts, this report shows that deteriorating youth mental health is a long-running trend that predates the COVID-19 pandemic, but that has intensified in recent years. The report highlights the complex, intersecting drivers behind this decline, from digitalisation and social media, to climate anxiety, fears about global conflicts, socioeconomic pressures, bullying and academic stress, and inequality and poverty. The report shows the importance of a comprehensive, multi-sectoral response including strengthening early prevention, improving access to low-threshold and peer-supported services, embedding socioemotional learning in schools, and developing balanced policies around digital technology. It also stresses the need for better, more frequent data collection and for listening directly to young people to understand their needs and priorities. The report aims to support OECD governments in designing more effective, evidence-informed strategies to stem the decline in young people’s mental health.