ADHD Is Linked to a Broad Burden of GI Symptoms

Although gastrointestinal (GI) symptoms are well documented in certain neurodevelopmental conditions like autism spectrum disorder, their relationship with attention-deficit/hyperactivity disorder (ADHD) has been less systematically characterized.

But a recent systematic review and meta-analysis found that ADHD was associated with significantly higher odds of a wide range of GI symptoms, including constipation, irritable bowel syndrome (IBS), diarrhea, abdominal pain, dyspepsia, and encopresis, compared with neurotypical controls.

A Broad Signal Across GI Symptoms

Researchers reviewed 9,613 records and included 23 studies spanning more than 1.9 million participants. The studies involved children and adults and comprised 16 cross-sectional studies, 6 retrospective cohort studies, and 1 case-control study; 21 of the 23 studies were judged to be of at least moderate methodological quality.

In the pooled analysis, ADHD was associated with 48% higher odds of total GI symptoms compared with neurotypical controls (OR 1.48, 95% CI [1.35, 1.62]). Additionally, significantly higher odds were observed across several individual GI outcomes, as outlined below:

• Constipation: OR 1.97 (95% CI [1.49, 2.61])
• Encopresis: OR 4.32 (95% CI [2.50, 7.47])
• IBS: OR 1.58 (95% CI [1.39, 1.78])
• Dyspepsia: OR 1.52 (95% CI [1.43, 1.61])
• Diarrhea: OR 2.18 (95% CI [1.52, 3.13])
• Abdominal pain: OR 1.88 (95% CI [1.07, 3.30])
• Unspecified stomach or bowel problems: OR 1.82 (95% CI [1.61, 2.07])

Flatulence was also reported more frequently in ADHD cohorts in the two available studies, although the data couldn’t be pooled in a meta-analysis.

Why Might ADHD and GI Symptoms Be Connected?

The review highlights several possible—and potentially overlapping—pathways.

Behavioral factors are one potential contributor. Emotional dysregulation and heightened stress reactivity may influence visceral sensitivity, while impulsive eating, irregular mealtimes, and selective food choices commonly associated with ADHD could affect GI function. Differences in interoceptive awareness may also play a role, particularly in constipation and encopresis.

The gut microbiome represents another possible pathway. Previous work has identified differences in microbial composition between people with ADHD and neurotypical controls. Therefore, the authors propose that gut dysbiosis, inflammation, and altered vagal signaling could contribute to GI symptoms, although these mechanisms remain hypothetical rather than established.

A third consideration is medication. Stimulants such as methylphenidate can cause GI adverse effects, including abdominal pain and nausea, and most studies in the review didn’t stratify findings by medication status. As a result, the investigators couldn’t determine how much of the observed symptom burden was intrinsic to ADHD versus treatment related.

What This Could Mean for Practice

Based on the findings, the authors argue that GI symptoms shouldn’t be overlooked in patients with ADHD. Healthcare professionals should routinely ask about GI symptoms during consultations and consider multidisciplinary input, including dietetic or gastroenterology support, in more complex cases.

At the same time, the review cannot establish causality. Publication bias couldn’t be assessed, several pooled analyses showed substantial heterogeneity, and many included studies didn’t account for medication effects or other confounding factors.

Therefore, the findings point to an association rather than a confirmed biological pathway. Future longitudinal research will be needed to not only determine whether GI symptoms precede ADHD, emerge as part of the condition, or are influenced by treatment, but also to clarify the relative roles of behavioral, microbial, neurobiological, and pharmacological factors.

Reference:
Blake S, Cannon H, Shantikumar S. The Association Between Attention-Deficit Hyperactivity Disorder and Gastrointestinal Symptoms: A Systematic Review and Meta-Analysis. J Atten Disord. Published online September 10, 2026. doi:10.1177/10870547261469626