The more urban an environment people live in the greater their risk for schizophrenia and the link remains even when age, sex, ethnicity, family history of psychosis and cannabis use are taken into account. One factor which is thought to be important is social capital; the levels of civic participation, social networks and trust in an area. A survey of 16,459 people in South London looked into the links between schizophrenia and social capital. It found that areas with low and high socil capital both had increased levels of schizophrenia. The researchers thought that this might be because the low-social-capital areas had less support available to compensate for the stresses of urban living. The higher incidence of schizophrenia in the higher-social-capital areas could be either because even though there are lots of social networks and a healthy civic society certain people are excluded from them or that, because there are better social networks and a higher level of social support people are more likely to be steered towards medical services when they become ill.
Kirkbride, J. ... [et al] - Testing the association between the incidence of schizophrenia and social capital in an urban area Psychological Medicine August 2008, 38(8), 1083-1094