Economic inequality and depressive symptoms: an individual versus aggregate-level analysis using Mexican survey data

There is a lack of consensus on the relationship between economic inequality and mental health, which may be due to the measures of inequality used in empirical studies. We studied this relationship using individual and aggregate measures of economic inequality, and tested whether there is an interaction between the individual and the aggregate levels.

We used data from a nationally representative Mexican health survey (Encuesta Nacional de Salud y Nutrición, n=44 324) where depressive symptoms were measured through a validated 7-item version of the Centre for Epidemiologic Studies Depression Scale. We estimated multilevel models employing aggregate inequality measures (Gini coefficient) and the individual-level framework of advantageous and disadvantageous inequality, where economic status comprised absolute wealth, relative deprivation and relative affluence.

The three facets of economic status were independently associated with depressive symptoms, while Gini coefficients showed no associations. Absolute wealth and relative affluence were associated with lower depressive symptoms while relative deprivation was associated with higher depressive symptoms. However, interaction models indicated an interplay between the Gini and relative affluence: higher status became a risk factor at high levels of aggregate economic inequality. For those at the top of the economic hierarchy, being in a context of high inequality more than doubles our measure of depressive symptoms-from 2.08 (95% CI 1.28 to 2.87) to 6.29 (95% CI 4.1 to 8.5) for state inequality and from 2.40 (95% CI 1.64 to 3.16) to 6.24 (95% CI 3.87 to 8.62) for municipal inequality.

We provided a novel perspective on the economic gradient in mental health, and on how high aggregate economic inequality may harm also the better off. Policymakers need to consider the consequences of economic inequalities, which can harm the mental health of both those at the bottom and the top of the socioeconomic ladder.