Health encompasses both physical and mental well-being.Yet for too long, mental health has been mostly an afterthought, despite its overwhelming impacts on communities and young people, everywhere.This year’s World Mental Health Day focuses on young people.One in five young people will experience a mental health problem this year. Half of all mental health conditions start by the age of 14. Most cases are, however, undetected and untreated.Poor mental health during adolescence has an impact on educational achievement and increases the risk of alcohol and substance use and violent behaviour. Suicide is a leading cause of death in young people. Millions of people are caught up in conflict and disasters, putting them at risk of a range of long-term mental health problems. Violence against women — physical, sexual and psychological — results in lasting scars, including post-traumatic stress disorder (PTSD). Yet despite these challenges, a great deal of mental health conditions are both preventable and treatable, especially if we start looking after our mental health at an early age. The 2030 Agenda is clear: We must leave no one behind. Yet, those struggling with mental health problems are still being marginalized. Healthy societies require greater integration of mental health into broader health and social care systems, under the umbrella of universal health coverage. The United Nations is committed to creating a world where by 2030 everyone, everywhere has someone to turn to in support of their mental health, in a world free of stigma and discrimination. If we change our attitude to mental health – we change the world. It is time to act on mental health.