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A Longitudinal Analysis of the Relationship between Neighbourhood Income Inequality and Maternal Mental Health in Calgary, Alberta
- Author / Creator
- Lowe, Samuel A J
Background – Emerging evidence has identified income inequality as a potential risk factor for adverse mental health outcomes. Previous research into the relationship between income inequality and mental health has been largely cross-sectional, with mixed results. Very few of these studies have focused on mothers or Canadian populations. This study addresses these gaps in current knowledge by analyzing longitudinal relationships between neighbourhood-level income inequality and anxiety and depressive symptoms among a cohort of pregnant and new mothers from Calgary, Alberta.
Study Design – This study involved secondary data analysis of an ongoing cohort of mothers and utilized a retrospective cohort study approach.
Methods – This thesis utilized longitudinal data collected from the All Our Families cohort study based in the city of Calgary, Alberta (Canada). From 2008 to 2014, respondents were asked to complete questionnaires at six time points, corresponding to <25 weeks of pregnancy to 3 years postpartum. Depressive symptoms were measured using the Edinburg Postnatal Depression Scale and the Centre for Epidemiological Studies-Depression Scale. Anxiety symptoms were measured using the Spielberger State Anxiety Inventory. Multilevel growth curve modeling was used to quantify the associations between neighbourhood-level income inequality (expressed as Gini coefficients) and anxiety and depressive symptoms over time, adjusting for individual and neighbourhood-level covariates. Outcomes were treated as both continuous and dichotomous in order to assess any subtle changes in anxiety and depressive symptoms (continuous) as well as the odds of experiencing elevated symptoms (dichotomous). Two sets of analyses were conducted: (1) with our full sample of mothers (n=2,461); and (2) excluding mothers who had elevated depressive symptoms (n=2,047) or elevated anxiety symptoms (n=2,047) at baseline to adjust for prior experience of elevated symptoms.
Results – The full sample of AOF mothers (n=2,461) had a high proportion of mothers who were white (78.9%) and married or common-law (94.6%), who had high household income (70.1%), and at least some post-secondary education (90.5%), and they tended to be older (mean age=30.7 years, SD=4.5 years). Over the course of follow-up, mean anxiety symptom scores ranged from 17.4-20.6 and peaked at 34-36 weeks of pregnancy, whereas mean depressive symptom scores ranged from 12.8-17.7 and peaked at baseline (<25 weeks of pregnancy). The prevalence of elevated anxiety symptoms and elevated depressive symptoms ranged from 15.0%-20.3% and 12.3%-16.8%, respectively, with a cumulative incidence of 267 cases/1,000 mothers for the first occurrence of elevated anxiety symptoms and 210 cases/1,000 mothers for the first occurrence of elevated depressive symptoms. For continuous anxiety, the models yielded a significant interaction term between neighbourhood Gini and time (β=0.0012, 95%CI=0.00020, 0.0023; p=0.020), indicating an excess rate of change over time. Specifically, a standardized deviation increase in Gini (z-score) was associated with an average monthly excess 1.0012% increase in mean anxiety symptom scores. This significant excess rate of change over time was also observed among mothers who did not report elevated anxiety symptoms at baseline (β=0.0017, 95%CI=0.00049, 0.0028; p=0.005), with a standardized deviation increase in Gini (z-score) associated with an average monthly excess 1.0017% increase in mean anxiety symptom scores. In spite of these excess rates of increase, linear combination estimates indicated that higher levels of income inequality were not associated with significantly higher anxiety symptom scores during the study period. While depressive symptom scores followed similar longitudinal trajectories across levels of income inequality, these analyses did not yield significant evidence for associations between inequality and depressive symptoms. There were also no significant associations between income inequality and dichotomous mental health outcomes, and no evidence of cross-level interactions between income inequality and household income for any study outcome.
Conclusion - This study provides evidence linking neighbourhood-level income inequality to changes in maternal mental health trajectories over time in an urban Canadian context. Further research should aim to uncover the specific mechanisms linking income inequality and mental health, and to understand how interventions intended to address income inequality might also promote better mental health and well-being.
- Graduation date
- Fall 2021
- Type of Item
- Master of Science
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.