To many, this provides evidence that cities are universally bad for our mental health—something that chimes with a strong cultural belief that associates the natural world with tranquillity. It might seem like common sense that living in a run-down, inner-city neighborhood would wear away at your psychological wellbeing. But here is where the cultural cliché breaks down, because the effect is surprisingly selective.

The data shows that urban environments reliably increase the chances of being diagnosed with schizophrenia or having related experiences like paranoia and hallucinations. This is not the case for other mental health problems primarily caused, for example, by depression or mood instability. If it was a general effect on wellbeing, you would expect the chance of being diagnosed with any mental health problem to increase at an equal rate, but this isn’t the case.

There are good reasons to think that city living might be the cause of some of these problems. The two big psychological negatives of city living, social isolation and social threat, are already well studied in mental health. They are risk factors for a range of psychological difficulties but have been particularly associated with misperceptions and paranoia. And for people who are already experiencing paranoid delusions, there is good evidence that urban environments amplify anxieties, increase the intensity of hallucinations, and weaken self-confidence.