Chronic Constipation Doubles Anorexia Risk, Study of 1.2 Million Patients Finds

Irritable bowel syndrome, chronic constipation, and functional dyspepsia may not just accompany eating disorders – they may help trigger them. A new retrospective cohort study published in Clinical and Translational Gastroenterology by Egboh SC and colleagues analyzed records from over 1.25 million UK general practice patients, finding significant associations between disorders of gut-brain interaction (DGBI) and eating disorders, with anxiety and depression playing a central linking role. The findings are emerging-level evidence, but the scale of the dataset gives them unusual weight.

Chronic Constipation and Anorexia Nervosa Share a Surprising Statistical Link

Among the 1,018 patients who carried both a DGBI and an eating disorder diagnosis, the associations were not evenly distributed across conditions. Chronic constipation stood out: patients with chronic constipation had roughly twice the odds of an anorexia nervosa diagnosis compared to those without it (odds ratio 2.12, 95% CI 1.84 to 2.45). The same pattern held for eating disorders broadly, with chronic constipation associated with any eating disorder at an odds ratio of 2.06 (95% CI 1.79 to 2.36). IBS and functional dyspepsia also showed significant associations with one or more eating disorders. The overall prevalence of any eating disorder in the cohort was 0.7%, which makes these two-fold elevations clinically meaningful. Research on gut microbiota imbalance and anxiety has separately shown that altered intestinal bacteria can feed back into behavior, immunity, and endocrinology, suggesting the gut-brain axis operates in multiple directions at once.

Eating Disorders More Often Came First, But the Relationship Runs Both Ways

The chronological data may be the study's most clinically useful contribution. In 59.5% of dual-diagnosis cases (606 patients), an eating disorder diagnosis preceded the DGBI diagnosis. In 40.5% (412 patients), the DGBI came first. That gap is statistically significant (P<0.001) and suggests that for the majority of affected patients, disordered eating behavior precedes the development of functional gut symptoms, not the other way around. Still, the 40% figure is large enough to matter: a substantial minority of patients may be developing eating disorders downstream of gut dysfunction. Anxiety disorders in DGBI patients are already known to reduce the likelihood of a positive response to gastrointestinal pharmacologic treatments, which makes accurate sequencing critical for designing interventions.

How the Researchers Identified Depression as a Key Predictor

The study drew from 1,256,331 patients in UK general practice records, a scale that provides statistical power difficult to achieve in controlled trials for these overlapping conditions. Of the 1,018 dual-diagnosis patients, 777 also had data on anxiety and/or depression, allowing the team to run multivariate models examining which factors independently predicted whether a DGBI would precede an eating disorder. Three independent predictors emerged: younger age at first DGBI diagnosis (P<0.001), antecedent depression (P<0.003), and prior use of proton pump inhibitors, or PPIs (P<0.001). The PPI finding is intriguing but not yet explained; PPIs alter gastric acid and may affect the gut microbiome in ways that influence downstream gut-brain signaling. The depression finding is more intuitive given what is known about the gut-brain axis in anorexia nervosa, where mood dysregulation and gastrointestinal symptoms are tightly intertwined.

Limitations of a Retrospective Cohort This Large

Retrospective general practice records carry inherent limitations. Diagnoses depend on what clinicians recorded, which means underdiagnosis of both eating disorders and DGBIs is likely, particularly for conditions like binge eating disorder that historically attract less clinical attention. The 1,018 dual-diagnosis patients represent a small fraction of the full cohort, and the 777 with psychological comorbidity data represent a further subset; selection effects cannot be ruled out. Causality cannot be inferred from association data alone, and the study design cannot distinguish between shared underlying vulnerabilities (genetic, microbiome-related, psychosocial) and true sequential causation. Significant literature gaps remain in understanding how gut microbiota contribute to anorexia and depression specifically, which limits how far these findings can be mechanistically interpreted. Similarly, the mechanisms linking binge-eating disorder to gut dysfunction remain largely unknown.

What Clinicians and Researchers Should Watch Next

The most immediate implication is clinical: gastroenterologists treating patients with IBS, functional dyspepsia, or chronic constipation should routinely screen for eating disorder history, and vice versa. The finding that depression independently predicts DGBI-first sequencing means that mental health history should factor into the clinical workup for both conditions. On the research side, prospective studies with standardized diagnostic criteria for both DGBIs and eating disorders, and fuller psychological assessments, are needed to test whether the associations here hold up under more controlled conditions. Researchers are already exploring microbiota-targeted eating disorder therapies, including probiotics and dietary modulation, as complements to conventional treatment; the sequencing data from this study could help identify which patients might benefit from gut-focused interventions earlier in their care.

Evidence rating

EMERGING — 76/100

Caveats:

• Retrospective observational design — shows associations, not causation; unmeasured confounders are likely.
• Only 1,018 patients had both diagnoses out of 1.25 million, limiting generalisability to people with co-occurring conditions.
• Diagnosis timing relies on GP records, which may not reflect true onset of symptoms.
• Funding was not disclosed by the authors, so independent verification of the funding source is not possible.
• Findings have not yet been independently replicated in a separate cohort.

Large retrospective cohort study drawing on 1,256,331 UK general practice records, with 1,018 patients carrying both a gut-brain disorder and an eating disorder diagnosis. The design establishes associations and chronological ordering but cannot determine causation, and findings rely on the completeness and accuracy of routine clinical records. The study has not yet been independently replicated.

References

1. SC Egboh, NA Koloski, MP Jones, A Shah, G Holtmann, NJ Talley (2026). ROLE OF ANXIETY AND DEPRESSION ON THE INTERPLAY BETWEEN DISORDERS OF GUT-BRAIN INTERACTION AND EATING DISORDERS. Clinical and Translational Gastroenterology. https://doi.org/10.14309/ctg.0000000000001025
2. Elisabet Navarro-Tapia, Laura Almeida-Toledano, Giorgia Sebastiani, Mariona Serra-Delgado, Óscar García-Algar, Vicente Andreu-Fernández (2021). Effects of Microbiota Imbalance in Anxiety and Eating Disorders: Probiotics as Novel Therapeutic Approaches. International Journal of Molecular Sciences. https://doi.org/10.3390/ijms22052351
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