Is urbanicity an environmental risk-factor for psychiatric disorders?

The link between urbanicity and the development of psychiatric disorders is well established. Recently, Kristina Sundquist and colleagues (2004) showed once again, with a strong study design, that there is a link between degree of urbanisation and first admission for psychosis. For men, the risk of first admission for psychosis was 68% higher in the most densely populated areas of Sweden than in the least densely populated areas (on a scale with five categories of urbanisation). For women, the risk was 77% higher. These results were all independent of age, marital status, education, and immigrant status. The results for psychosis contrast with the weak correlations found for depression (12% higher for men and 20% higher for women). Possible explanations given by the investigators for the increased risk in cities compared with rural areas are differences in social support, stressful life events, and familial liability.