# Dietary inflammation and socioeconomic status mediate depression–constipation link: a cross-sectional analysis of NHANES 2005–2010

## TL;DR

This study finds that depression and constipation are linked, with diet and socioeconomic factors playing a mediating role, using data from a large U.S. health survey.

## Contribution

The study reveals a non-linear relationship between depression and constipation, partially mediated by dietary inflammation and socioeconomic status.

## Key findings

- Depression severity is independently associated with constipation risk, with a non-linear relationship peaking at PHQ-9 score of 10.
- Dietary inflammation (DII) and socioeconomic status (PIR) mediate 6.03% and 12.46% of the depression-constipation link, respectively.
- The association between depression and constipation remains consistent across all demographic and clinical subgroups.

## Abstract

This study investigated the relationship between depression and constipation and examined potential mediating roles of dietary inflammatory index (DII) and socioeconomic status using data from NHANES 2005–2010.

We analyzed 12,854 adults with complete data on depression (PHQ-9), constipation (self-report/Bristol Stool Scale), DII (27 nutrients), and poverty-to-income ratio (PIR). Statistical analyses included multivariable logistic regression with appropriate reference categories, restricted cubic splines (RCS), mediation analysis, and subgroup assessments.

Constipated individuals exhibited significantly higher depression severity (mean PHQ-9: 4.25 vs. 3.00), higher DII (2.00 vs. 1.37), and lower PIR (all p < 0.0001). After adjustments, PHQ-9 scores were independently associated with constipation risk (OR: 1.04, 95% CI: 1.03–1.06), with a non-linear relationship showing an inflection point at PHQ-9 = 10 (scores <10: OR = 1.08; scores ≥10: OR = 0.98). Statistical mediation analysis revealed that DII mediated 6.03% and PIR mediated 12.46% of the depression–constipation association. Subgroup analyses demonstrated consistent associations across all demographic and clinical subgroups (OR range: 1.04–1.14).

This cross-sectional study demonstrates a significant non-linear relationship between depression and constipation, partially mediated by dietary inflammation and socioeconomic status. Longitudinal studies are needed to establish causality and directionality between these variables.