Over the past decade, a number of bodies have published thought-provoking data on mental health. Some of these reports have identified that levels of mental distress are rising across the western world and — more controversially — that there is a stark difference between nations.

According to the World Health Organization, almost 25 per cent of the US population has suffered from mental stress, while in Australia, the UK, New Zealand and Canada the level hovers around 20 per cent. In Japan, the figure is below 10 per cent; so too in Germany, Spain and Italy — well below the US level.

Why? An anthropologist might attribute this to different cultural concepts of individualism, happiness and self-expression. An economist might point to differing commercial incentives: in a country such as the US, where private sector companies make money by selling antidepressant drugs, there are profits to be made by increasing the proportion of reported and self-reported people suffering from “stress”, “anxiety” or “depression”.