In the latest issue of the journal Nature, science writer Alison Abbott surveys recent research that tests the link between urban stress and psychosis. The association makes sense — cities are stressful places, and stress plays a known role in mental health problems — but remains hard to isolate for obvious reasons. "It is difficult to study whether something as complex as a 'city environment' has an impact on the brain," writes Abbott.
A number of studies have narrowed in on the city-psychosis relationship in the past 20 years. Scientists have found that rates of schizophrenia are higher in people brought up in the city compared to the country, that people simply born with a higher "degree of urbanization" showed an increased risk, and that family history for the illness makes those in a city environment even more vulnerable. Some researchers feel comfortable enough suggesting a "causal association" between cities and psychosis: the more early years you spend in cities, the greater your risk for mental disorder.