Research Summary

Soft Drink Intake Linked to MDD Diagnosis and Severity, Partly Mediated by Eggerthella in Women

Kate Young

Key Highlights

  • Soft drink consumption was associated with higher odds of major depressive disorder (MDD) diagnosis and greater symptom severity in a German multicenter cohort.
  • Associations were stronger in women and were not significant in men.
  • In women, higher soft drink intake correlated with increased gut Eggerthella abundance and lower alpha-diversity; Eggerthella significantly mediated the soft drink–MDD link.
  • Findings persisted with adjustment for site, education, library size, BMI, and total calorie intake in sensitivity analyses.

According to the researchers of a recent cross-sectional study, soft drink consumption may be linked to major depressive disorder (MDD) diagnosis and increased depressive symptom severity, with significant associations observed only among women. Indeed, among women, soft drink intake correlated with higher gut Eggerthella abundance and lower microbial alpha-diversity. These associations remained significant after adjustment for site, education, BMI, and total caloric intake.

Prior work has linked soft drinks to adverse mental and physical outcomes and implicates gut microbiota in MDD; however, evidence connecting soft drink intake with clinically diagnosed MDD and mechanistic microbiome pathways has been limited.

Investigators analyzed cross-sectional data from the Marburg–Münster Affective Cohort in Germany, including adults aged 18–65 years recruited from the general population and primary care (September 2014–September 2018). The sample comprised 405 patients with MDD and 527 healthy controls.

Soft drink intake was quantified via a validated 101-item food frequency questionnaire. Depressive symptoms were assessed with the Beck Depression Inventory (BDI-I). Stool 16S rRNA sequencing characterized microbial taxa; analyses focused a priori on Eggerthella and Hungatella. Multivariable logistic regression and ANOVA examined associations with MDD diagnosis and severity, adjusting for site and education; models of microbiota additionally adjusted for library size. Mediation analyses (bootstrap/permutation, 10,000 permutations) tested whether bacterial abundance mediated soft drink–MDD associations. Sensitivity analyses added BMI; additional checks addressed medication status, total calorie intake, and exclusion of eating disorders.

Among 932 participants (MDD: mean [SD] age, 36.37 [13.33] years; 67.9% women; controls: 35.33 [13.13] years; 65.5% women), higher soft drink consumption predicted MDD diagnosis (OR, 1.081; 95% CI, 1.008-1.159; P = .03) and greater symptom severity (P < .001; ηp², 0.012; 95% CI, 0.004-0.035). Effects were stronger in women (diagnosis: OR, 1.167; 95% CI, 1.054-1.292; P = .003; severity: P < .001; ηp², 0.036; 95% CI, 0.011-0.062) and non-significant in men. In women, soft drink intake was associated with higher Eggerthella abundance (P = .007; ηp², 0.017) but not Hungatella (P = .57), and with lower alpha-diversity (P = .001; ηp², 0.025). Mediation analyses in women indicated Eggerthella accounted for a portion of the soft drink–MDD association (diagnosis: P = .011; ~3.82% of total effect; severity: P = .005; ~5.00%). Results were robust when controlling for BMI and when normalizing soft drink calories to total caloric intake; excluding participants with eating disorders did not alter conclusions.

“In this cohort study, it was found that soft drink consumption may contribute to MDD through gut microbiota alterations, notably involving Eggerthella,” the study authors concluded. “Public health strategies to reduce soft drink intake may help mitigate depression risk, especially among vulnerable populations; in addition, interventions for depression targeting the microbiome composition appear promising.”

Reference:
Edwin Thanarajah S, Ribeiro AH, Lee J, et al. Soft Drink Consumption and Depression Mediated by Gut Microbiome Alterations. JAMA Psychiatry. Published online September 24, 2025. doi:10.1001/jamapsychiatry.2025.2579