ADHD Linked to Increased Digestive Problems in Massive 1.9 Million-Person Study - Video

An analysis has found an association between attention-deficit/hyperactivity disorder (ADHD) and digestive problems, suggesting that gut symptoms may warrant attention when caring for people with ADHD.

Researchers at the University of Warwick reviewed 23 studies involving more than 1.9 million people from the United States, Sweden, Germany and South Korea. Participants ranged from 2 to 65 years old. The review, published in the Journal of Attention Disorders, is the first systematic review specifically examining gastrointestinal symptoms in ADHD.

Overall, people with ADHD were almost 50% more likely to experience gastrointestinal symptoms than people without ADHD. The strongest associations were seen for constipation, irritable bowel syndrome (IBS) and encopresis, or loss of bowel control. People with ADHD had nearly twice the odds of constipation, 58% higher odds of IBS and more than four times the odds of encopresis.

Researchers say several factors could contribute to the connection. ADHD-related impulsivity, irregular eating patterns and dietary habits may affect digestion. Medicines used to treat ADHD can also cause gastrointestinal side effects, including constipation.

The gut microbiome may provide another possible explanation. Previous research has reported differences in gut bacteria among people with ADHD. These microbes can influence communication between the digestive system and brain through pathways including the vagus nerve. However, these mechanisms remain under investigation.

The researchers say clinicians should ask people with ADHD about digestive symptoms, particularly when symptoms affect daily life. Patients may also benefit from advice from a qualified dietitian.

Importantly, the findings show an association and do not prove that ADHD causes gastrointestinal problems. The review also cannot establish whether symptoms are driven mainly by ADHD-related behaviours, medications, biological factors or other influences.

Further research is needed to understand the ADHD-gut connection and determine whether addressing digestive health could improve wellbeing.

REFERENCE: Sarah Blake, Hugo Cannon, Saran Shantikumar. The Association Between Attention-Deficit Hyperactivity Disorder and Gastrointestinal Symptoms: A Systematic Review and Meta-Analysis. Journal of Attention Disorders, 2026; DOI: 10.1177/10870547261469626