By: IPP Bureau
Last updated : September 14, 2026 4:30 pm
The study by University of Warwick researchers is the first systematic review to specifically examine gastrointestinal symptoms in people with ADHD
Researchers at the University of Warwick have found a strong association between attention-deficit/hyperactivity disorder (ADHD) and gastrointestinal symptoms after analysing data from more than 1.9 million people across 23 studies.
The systematic review found that people with ADHD had an almost 50% higher likelihood of experiencing gastrointestinal symptoms compared with those without ADHD.
The association was stronger for specific conditions, with nearly twice the odds of constipation, a 58% higher likelihood of irritable bowel syndrome (IBS), and more than four times the odds of encopresis, or loss of bowel control.
Published in the Journal of Attention Disorders, the study is the first systematic review to specifically examine gastrointestinal symptoms in people with ADHD. The research included studies from countries including the US, Sweden, Germany and South Korea and covered individuals aged between two and 65 years.
“Almost every gut symptom we looked at: constipation, IBS, even indigestion, appeared to be associated with ADHD. These symptoms can have a real impact on daily life, but they could easily be overlooked if the focus is on ADHD itself,” said Sarah Blake, co-lead author and Medical Student at Warwick Medical School.
The researchers said several factors could potentially explain the association. ADHD-related behaviours, including impulsivity and irregular eating patterns, may influence digestive health, while some ADHD medications can cause gastrointestinal side effects such as constipation. Differences in gut bacteria associated with ADHD may also play a role through the gut-brain axis and the vagus nerve, which facilitates communication between the digestive system and brain.
The study estimated that ADHD affects around 5% of children and 3-4% of adults worldwide. While gastrointestinal problems are already well documented in autism spectrum disorder, the extent of such symptoms in ADHD has been less clear.
The researchers stressed that the findings demonstrate an association and do not establish that ADHD causes gastrointestinal problems. They called for further research to distinguish biological mechanisms from medication-related and behavioural factors.
“Clinicians caring for people with ADHD may want to consider asking about gastrointestinal symptoms, particularly if they may be affecting quality of life,” said Dr Saran Shantikumar, Associate Clinical Professor, Warwick Medical School.