Poor mental health affects more than one in five people across OECD and EU27 countries and is estimated to reduce healthy life expectancy by 2.5 years, with young people, women, and those with low socio?economic status particularly affected. Focusing on depression and anxiety, this report sets out the strong economic case for investing in better mental health policies. It shows how evidence?based interventions in primary care, schools, and workplaces can improve health outcomes and boost economic growth through improved productivity and labour market participation. Many of these interventions are cost?effective and some cost?saving. However, the overall impact of these interventions remains low due to lack of implementation at scale. To deliver meaningful improvements, countries must adopt a more systemic approach that enhances intervention design and implementation, expands coverage and investment and tackles the root causes of mental distress.