Inequality within a community at the neighborhood level and the incidence of mood disorders in Japan: a multilevel analysis

The association between income inequality and adult mental health at the subnational level-a systematic review

PURPOSE

A systematic review was undertaken to determine whether research supports: (i) an association between income inequality and adult mental health when measured at the subnational level, and if so, (ii) in a way that supports the Income Inequality Hypothesis (i.e. between higher inequality and poorer mental health) or the Mixed Neighbourhood Hypothesis (higher inequality and better mental health).

METHODS

Systematic searches of PsycINFO, Medline and Web of Science databases were undertaken from database inception to September 2020. Included studies appeared in English-language, peer-reviewed journals and incorporated measure/s of objective income inequality and adult mental illness. Papers were excluded if they focused on highly specialised population samples. Study quality was assessed using a custom-developed tool and data synthesised using the vote-count method.

RESULTS

Forty-two studies met criteria for inclusion representing nearly eight million participants and more than 110,000 geographical units. Of these, 54.76% supported the Income Inequality Hypothesis and 11.9% supported the Mixed Neighbourhood Hypothesis. This held for highest quality studies and after controlling for absolute deprivation. The results were consistent across mental health conditions, size of geographical units, and held for low/middle and high income countries.

CONCLUSIONS

A number of limitations in the literature were identified, including a lack of appropriate (multi-level) analyses and modelling of relevant confounders (deprivation) in many studies. Nonetheless, the findings suggest that area-level income inequality is associated with poorer mental health, and provides support for the introduction of social, economic and public health policies that ameliorate the deleterious effects of income inequality.

CLINICAL REGISTRATION NUMBER

PROSPERO 2020 CRD42020181507.

Is neighbourhood income inequality associated with maternal mental health? A longitudinal analysis of pregnant and new mothers living in Calgary, Alberta

OBJECTIVES

Rising income inequality is a potential risk factor for poor mental health, however, little work has investigated this link among mothers. Our goal was to determine if neighbourhood-level income inequality was associated with maternal mental health over time.

DESIGN

Secondary data analysis using a retrospective cohort study design.

SETTING AND PARTICIPANTS

Data from the All Our Families (AOF) ongoing cohort study in the city of Calgary (Canada) were used, with our sample including 2461 mothers. Participant data were collected at six time points from 2008 to 2014, corresponding to <25 weeks of pregnancy to 3 years post partum. AOF mothers were linked to 196 geographically defined Calgary neighbourhoods using postal code information and 2006 Canada Census data.

MAIN OUTCOME MEASURES

Anxiety symptoms measured using the Spielberger State Anxiety Inventory, and depressive symptoms measured using the Edinburgh Postnatal Depression Scale and the Centre for Epidemiologic Studies-Depression Scale.

RESULTS

Multilevel regression modelling was used to quantify the associations between neighbourhood-level income inequality and continuous mental health symptoms over time. For anxiety symptoms, the interaction term between neighbourhood Gini and time was significant (β=0.0017, 95% CI=0.00049 to 0.0028, p=0.005), indicating an excess rate of change over time. Specifically, a SD increase in Gini (Z-score) was associated with an average monthly rate increase in anxiety symptom scores of 1.001% per month. While depressive symptom scores followed similar longitudinal trajectories across levels of income inequality, we did not find significant evidence for an association between inequality and depressive symptoms. There was no evidence of a cross-level interaction between inequality and household income on either outcome.

CONCLUSION

Income inequality within neighbourhoods appears to adversely impact the mental health trajectories of pregnant and new mothers. Further research is needed to understand the mechanisms that explain this relationship, and how interventions to reduce income inequality could benefit mental health.