Soda and Depression: The Hidden Role Of Gut Bacteria

This study shows that frequent soft drink consumption is linked to an increased risk and severity of major depression, especially in women. This association occurs, in part, because soft drinks alter the gut microbiota, increasing the abundance of Eggerthella bacteria, which contributes to inflammation and worsening depressive symptoms.

In recent years, soft drink consumption has become one of the most common dietary habits worldwide. It is estimated that more than 1.9 billion people consume sugary drinks daily, including traditional soft drinks, and this number is growing especially among young people and in low- and middle-income countries.

Reports from the World Health Organization show that in some countries, each person consumes an average of more than 100 liters of soft drinks per year. This excessive consumption is strongly linked to chronic diseases such as obesity, type 2 diabetes, heart problems, and even cancer.

In recent years, researchers have also drawn attention to the negative effects of soft drinks on mental health, suggesting a possible link with anxiety, mood swings, and depression. Despite this evidence, little is known about the biological mechanisms that may explain this connection between soft drinks and mental disorders.

This study sought to answer an important question: is soft drink consumption linked to the risk of developing major depressive disorder (MDD)? And, if so, does this association occur because soft drinks alter the gut microbiota, that is, the bacteria that live in our intestines? The scientists focused on two specific bacteria: Eggerthella and Hungatella, which previous studies had already linked to inflammatory problems and mood swings.

To investigate this question, researchers in Germany conducted a large study called the Marburg-Münster Affective Cohort, conducted between 2014 and 2018. They analyzed 405 people diagnosed with major depression and compared them with 527 healthy individuals, all between 18 and 65 years of age.

Participants were recruited from both the general population and primary health care settings. Statistical analyses were conducted later, between May and December 2024, when the data were processed in detail.

The method used was quite rigorous. First, all participants completed detailed questionnaires about their dietary habits and soft drink consumption. Clinical examinations and laboratory tests were then performed, including fecal samples to measure the number of different bacteria in the gut microbiota.

Eggerthella lenta

To ensure that the results were not influenced by other factors, the scientists controlled for variables such as education level, collection location, and even the size of the genetic library analyzed (meaning they adjusted the data to avoid technical biases in the bacterial measurements).

In the statistical analysis, they used two main methods: multivariate regression models (to determine whether soda consumption increased the chances of depression, even when accounting for other factors) and ANOVA (to analyze differences between groups and the severity of depression symptoms). They also performed mediation analyses: this means they tested whether a greater or lesser presence of Eggerthella and Hungatella bacteria could explain the relationship between soda and depression.

The results were very revealing. People who consumed more soda had a higher risk of depression and also had more severe symptoms. This effect was stronger in women, whose risk increased even more. Among women, it was also observed that soda consumption was associated with a greater abundance of Eggerthella bacteria in the gut, but not of Hungatella.

Mediation analysis confirmed that Eggerthella was responsible for explaining a significant portion of the relationship between soft drinks and depression, reaching 5% of the total effect on symptom severity.

These findings suggest that it's not just the sugar or additives in soda that directly affect mental health, but also how these substances interact with the gut microbiota. Changes in the balance of gut bacteria can influence inflammation, neurotransmitter production, and, consequently, mood and depressive symptoms.

In summary, the study shows that reducing soda consumption may not only protect against physical illnesses but also reduce the risk of depression, especially among women. Furthermore, it suggests that new therapies for depression could focus on the gut microbiome, whether with probiotics, diet, or specific interventions to modulate bacteria such as Eggerthella.

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Soft Drink Consumption and Depression Mediated by Gut Microbiome Alterations

Sharmili  Edwin Thanarajah, Adèle H. Ribeiro,  Jaehyun Lee, Nils R. Winter, Frederike Stein, Rachel N. Lippert,  Ruth Hanssen, 

Carmen Schiweck, Leon Fehse, Mirjam Bloemendaal, Mareike Aichholzer, 

Aicha Bouzouina, Carmen Uckermark, Marius Welzel, Jonathan Repple, 

Silke Matura, Susanne Meinert, Corinna Bang, Andre Franke, 

Ramona Leenings, Maximilian Konowski, Jan Ernsting, Lukas Fisch, Carlotta Barkhau, Florian Thomas-Odenthal,Paula Usemann, Lea Teutenberg, 

Benjamin Straube, Nina Alexander, Hamidreza Jamalabadi, Igor Nenadić, 

Andreas Lügering, Robert Nitsch, Sarah Kittel-Schneider, John F. Cryan, 

Andreas Reif, Tilo Kircher,  Dominik Heider, Udo Dannlowski,and Tim Hahn. 

JAMA Psychiatry. Published Online: September 24, 2025

doi: 10.1001/jamapsychiatry.2025.2579

Abstract: 

Soft drink consumption is linked to negative physical and mental health outcomes, but its association with major depressive disorder (MDD) and the underlying mechanisms remains unclear. To examine the association between soft drink consumption and MDD diagnosis and severity and whether this association is mediated by changes in the gut microbiota, particularly 

Eggerthella and Hungatella abundance. This multicenter cohort study was conducted in Germany using cross-sectional data from the Marburg-Münster Affective Cohort. Patients with MDD and healthy controls (aged 18-65 years) recruited from the general population and primary care between September 2014 and September 2018 were analyzed. Data analyses were conducted between May and December 2024. Primary analyses included multivariable regression and analysis of variance (ANOVA) models examining the association between soft drink consumption and MDD diagnosis and symptom severity, controlling for site and education, and Eggerthella and Hungatella abundance,

controlling for site, education, and library size. Mediation analyses tested whether microbiota abundance mediated the soft drink–MDD link. A total of 405 patients with MDD (275 female patients [67.9%]; mean [SD] age, 36.37 [13.33] years) and 527 healthy controls (345 female controls [65.5%]; mean [SD] age, 35.33 [13.13] years) were included. Soft drink consumption predicted MDD diagnosis (odds ratio [OR], 1.081; 95% CI, 1.008-1.159; P = .03) and symptom severity (P < .001; partial η2 [ηp2], 0.012; 95% CI, 0.004-0.035), with stronger effects 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). In women, consumption was linked to increased Eggerthella (P = .007; ηp2, 0.017; 95% CI, 0.0002-0.068), but not Hungatella abundance. Mediation analyses confirmed that Eggerthella 

significantly mediated the soft drink–MDD association (diagnosis: P = .011; severity: P = .005), explaining 3.82% and 5.00% of the effect, respectively. In this cohort study, it was found that soft drink consumption may contribute to MDD through gut microbiota alterations, notably involving Eggerthella. 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.