Exploring the causal nature of neighborhood influences on violent criminality, substance misuse and psychiatric morbidity

Abstract

Individuals who live in socioeconomically deprived neighborhoods, particularly in urban settings, experience elevated risk of being convicted of violent criminality, to engage in substance misuse and to be diagnosed with psychiatric disorders. The causal nature of these associations is questioned in the literature because previous studies have insufficiently accounted for genetic and environmental risks shared within families. The aim of the dissertation was therefore to explore the etiological relevance of neighborhoods in these traits by combining quasi-experimental, family-based research designs with nationwide Swedish registry data.

In Studies I and II, we investigated the associations between residence in deprived neighborhoods and family income during childhood on subsequent risks of being convicted of violent offences and to engage in substance misuse. We found that biological full-siblings who had been differentially exposed to deprived neighborhoods, due to residential relocations between their birthdays, or to family income, due to the parents’ career trajectories, did not differ from one another in terms of their risks for being convicted or to engage in substance misuse.

In Study III, we studied the associations between neighborhood deprivation and population density on later risks of being diagnosed with schizophrenia. Biological full-siblings who had been differentially exposed to the different neighborhood conditions did not differ from one another in terms of their risks of schizophrenia.

In Study IV, we used quantitative genetic models that compared biological full and half-siblings to understand the etiology of social drift in schizophrenia. We found that the heritability of living in deprived neighborhoods was 60 percent. Schizophrenia patients were more likely to live in deprived neighborhoods but this was due to common genetic influences.

In conclusion, we found that familial risks simultaneously explained parental selection into high-risk neighborhoods as well as their offspring’s increased risks of adverse outcomes. Methodologically, these studies emphasize the importance of accounting for unobserved familial confounders in epidemiological studies of socioeconomic status and later behavioral and psychiatric outcomes. Substantively, the findings indicate that efficient prevention efforts to decrease the rates of the examined outcomes must consider a broader range of familial and individual risks than merely socioeconomic and demographic measures, at least in the Swedish context.