How Income and Income Inequality Drive Depressive Symptoms in U.S. Adults, Does Sex Matter: 2005–2016

Importance: Depression is one of the leading causes of disability in the United States. Depression prevalence varies by income and sex, but more evidence is needed on the role income inequality may play in these associations. Objective: To examine the association between the Poverty to Income Ratio (PIR)—as a proxy for income—and depressive symptoms in adults ages 20 years and older, and to test how depression was concentrated among PIR. Design: Using the 2005–2016 National Health and Nutrition Examination Survey (NHANES), we employed Negative Binomial Regression (NBRG) in a sample of 24,166 adults. We used a 9-item PHQ (Public Health Questionnaire, PHQ-9) to measure the presence of depressive symptoms as an outcome variable. Additionally, we plotted a concentration curve to explain how depression is distributed among PIR. Results: In comparison with high-income, the low-income population in the study suffered more from greater than or equal to ten on the PHQ-9 by 4.5 and 3.5 times, respectively. The results of NBRG have shown that people with low-PIR (IRR: 1.30, 95% CI: 1.23–1.37) and medium-PIR (IRR: 1.55, 95% CI: 1.46–1.65) have experienced a higher relative risk ratio of having depressive symptoms. Women have a higher IRR (IRR: 1.29, 95% CI: 1.24–1.34) than men. We observed that depression was concentrated among low-PIR men and women, with a higher concentration among women. Conclusion and Relevance: Addressing depression should target low-income populations and populations with higher income inequality.