Key Insights on Income Inequality and Health

A large body of literature examines the relationship between income inequality and health, indicating worse health outcomes in more unequal societies.
Recent studies reinforce the evidence of a causal link between income differences and various health issues, including violence.

Evidence supports that income inequality negatively affects population health and wellbeing, meeting various criteria for causality: temporality, biological plausibility, consistency, and lack of alternative explanations.
Most studies showing no association can be attributed to inappropriate measurement scales, subjective health measures, or short follow-up periods.

The hypothesis linking inequality to poor health has roots in criminology and sociology, with significant studies done over the last 40 years.
The notion has evolved to include not just physical health but also mental health and societal issues related to social status disparity.

Consistency: Approx. 300 studies support a link between income inequality and health outcomes, with variations in results stemming from geographic scale.
Temporality: Many studies establish that changes in income inequality precede changes in health.
Strength of Association: Higher correlations found in mental health and teenage birth rates compared to infant mortality.
Specificity: Outcomes with a clear social gradient tend to have links with income inequality.
Dose-Response Relationship: Evidence suggests that greater inequality consistently correlates with poorer health outcomes.
Cessation of Exposure: Evidence from studies on immigrants shows that moving to more equitable environments correlates with improved health.

Prior studies suggesting ethnicity or individual income explains the income inequality-health association have been disproven by more recent analyses which confirm contextual effects of inequality.
The relationship holds even when accounting for factors like ethnic heterogeneity.

Reducing income inequality can lead to better population health outcomes, and significant health improvements could result from lowering the Gini coefficient.