There are many reasons why mental wellbeing is important. Not only is it protective against physical illnesses and linked to greater productivity, but the mental wellbeing of a population is essential for a country’s sustainability, long-term growth and development. But despite the clear benefits, governments tend to focus public spending on treating and preventing disease, and providing care for those who are ill. While this is important and should continue to be prioritised, such strategies alone won’t increase levels of mental wellbeing overall. In our latest study, we explored the link between mental wellbeing and government expenditure. We found that each increase in mental wellbeing in a population was associated with lower health and social care costs the following year. In other words, the greatest savings could be made by maximising everyone’s mental wellbeing.