Urbanicity and Risk of Schizophrenia—New Studies and Old Hypotheses

Abstract

Every man, wherever he goes, is encompassed by a cloud of comforting convictions, which move with him like flies on a summer day.

Association Between Population Density and Genetic Risk for Schizophrenia

“…Our findings support the notion that the increased schizophrenia prevalence in urbanized areas is not only owing to the environmental stressors of the city or other putative risk factors associated with urbanicity (eg, increased risk of infection, low vitamin D levels, and substance abuse) 49 but also on the genetic risk for the disease. The associated PRS prediction was replicated across 3 different countries that likely differ in availability of space, social mobility/opportunities, associations between population density and SES of the area, and historical constraints on living environment.…”

“…Furthermore, we provide evidence that schizophrenia genetic risk may lead to individuals (or had led to their ancestors) seeking denser/urban and low socioeconomic status neighborhoods, which could in turn be risk factors for the disease. 1,2,49 Future disease models will need to include both genetic selection and environmental factors of urban stress on schizophrenia to inform implications for intervention. In addition, there is a need to address the potential gene-by-environment interactions that would arise if genetic variants influencing schizophrenia also influence the choice of a stressful neighborhood, which would contribute to the interaction between urbanicity and family history of schizophrenia that has been reported in the Danish population.…”

The Complexities of Evaluating the Exposome in Psychiatry: A Data-Driven Illustration of Challenges and Some Propositions for Amendments

“…15 Urbanicity may be associated with psychosis in high-income countries but not in developing countries. 16 This inconsistency may be explained primarily by the variation of other factors linked to urbanicity across different settings, such as ethnic density, substance use practices, patterns of pollution, and infectious agents, 17 which are elements of the wider totality of exposures, the "exposome." To validate both the association signal and the heterogeneity, the entirety of the available exposures ("exposome") need to be evaluated agnostically in each study/dataset, instead of taking the easy (profitable for "salami slicing" publications) way out of 1-exposure to 1-outcome at a time analysis using the same single dataset and selective reporting.…”

Women who suffer from schizophrenia: Critical issues

“…Further theoretical possibilities for prevention (based entirely on studies of association) are keeping children in their country of birth, since migration is a risk factor for schizophrenia[ 30 , 31 ], residing in rural rather than urban parts of the country[ 32 , 33 ], keeping children and adolescents away from alcohol and drugs[ 34 ] and teaching them emotion-regulating strategies (reappraising, accepting, and refocusing[ 35 ]) to prevent adversities such as discrimination and social defeat from culminating in paranoid delusions[ 36 ].…”