Mental health is an important driver of labour market outcomes and thus affects economic growth and future development. In OECD countries, mental ill-health is responsible for between one-third and one-half of all long-term sickness and disability among the working-age population. It causes and exacerbates chronic physical illness, pushing up health care costs. And it lowers education outcomes – partly because those who are ill leave school early – so shutting off employment opportunities. Relatively to the mentally healthy, the employment rate of people who suffer from poor mental health is 15-30 percentage points lower and their unemployment rate is twice as high. They are also twice as likely to live in poor households. In the workplace, employees who suffer from mental ill-health tend to underperform and their low productivity is probably the single biggest cost factor, borne to a large extent by employers.