Background Depression is an important contributor to the global burden of disease. Besides several known individual-level factors that contribute to depression, there is a growing recognition that neighbourhood environment can also profoundly affect mental health. This study assessed associations between three neighbourhood constructs—socioeconomic deprivation, residential instability and income inequality—and depression among adult twin pairs. The twin design is used to examine the association between neighbourhood constructs and depression, controlling for selection factors (ie, genetic and shared environmental factors) that have confounded purported associations.
Methods We used multilevel random-intercept Poisson regression among 3738 same-sex twin pairs from a community-based twin registry to examine the association between neighbourhood constructs and depression. The within-pair association controls for confounding by genetic and environmental factors shared between twins within a pair, and is the main parameter of interest. Models were adjusted for individual-level income, education and marital status, and further by neighbourhood-level population density.
Results When twins were analysed as individuals (phenotypic model), all neighbourhood constructs were significantly associated with depression. However, only neighbourhood socioeconomic deprivation showed a significant within-pair association with depression. A 10-unit within-pair difference in neighbourhood socioeconomic deprivation was associated with 6% greater depressive symptoms (1.06, 95% CI 1.01 to 1.11); the association did not substantially change in adjusted models.
Conclusion This study provides new evidence linking neighbourhood socioeconomic deprivation with greater depression. Future studies should employ longitudinal designs to better test social causation versus social selection.
- social inequalities
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Contributors HC-C and GED formulated the original research questions and designed the study. HC-C and GED were responsible for and provided the data. Critical input from WEB, SAAB, JW and RLM refined the research questions, methods and analyses as part of HC-C’s doctoral dissertation. HC-C analysed the data with guidance from JW and a consultant. HC-C drafted the manuscript with critical input and feedback on all aspects of data interpretation and subsequent manuscript versions from all authors.
Funding This research was supported in part by grants from the NIH (R01AG042176 to GED and RC2HL103416 to Buchwald). JW was supported by a grant from the NIH (R01CA095994).
Competing interests None declared.
Patient consent Obtained.
Ethics approval University of Washington Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.