- A recent review of available research concluded that people with an ADHD diagnosis have 48% increased odds of experiencing gastrointestinal symptoms.
- This adds to a growing body of research linking gastrointestinal issues to mental and psychiatric disorders.
- Experts have a few theories about what might be behind this correlation.
Our brain and our gut might be more closely related than they’d appear at first glance. Depression has been linked to an increased risk of irritable bowel syndrome (IBS), gastroesophageal reflux (GERD), ulcers, and more; people with inflammatory bowel disease (IBD) are more likely to suffer from psychiatric disorders; and researchers have found people with obsessive-compulsive disorder (OCD) often have alterations in the gut microbiome.
Now, a new review suggests that people with attention-deficit/hyperactivity disorder (ADHD) are much more likely to report gastrointestinal symptoms. The paper, published in the Journal of Attentional Disorders, linked ADHD to an increased likelihood of every gastrointestinal issue researchers investigated, from IBS to constipation.
“Earlier research had already linked ADHD with IBS. Our review builds on that work by bringing together evidence focused on a range of individual gut symptoms and functional problems, including symptom reports as well as recorded diagnoses,” says lead author Sarah Blake, M.B.Ch.B.
In part, personal experience led Blake to investigate this link. Not only did she get relief from myalgic encephalitis/chronic fatigue syndrome (ME/CFS) through diet changes as a child, but as an adult, she was diagnosed with both IBS and ADHD—the former at 18, and the latter at 25. “Living with both conditions made me realize how frequently my neurodivergent friends struggled with gut issues while being young and healthy,” she says.
Meet the Experts: Sarah Blake, M.B.Ch.B., lead study author and resident doctor in the UK’s National Health Service (NHS); Hugo Cannon, M.B.Ch.B., study co-author and resident doctor in the UK’s NHS.
While ADHD is often associated with kids, it’s actually remarkably common to receive a diagnosis later in life. In fact, a 2023 report from the Centers for Disease Control (CDC) found that about half of U.S. adults with ADHD had been diagnosed in adulthood—meaning the researchers’ findings about the link between ADHD and gastrointestinal issues apply to a broader swathe of the population than you might think.
So, what’s behind this connection, and what does it mean for people living with ADHD? Ahead, the co-authors of the review break it down.
What did the study find?
The review analyzed data from 23 studies, which included over 1.9 million total participants. After crunching the numbers, the researchers found that an ADHD diagnosis was linked to a 48% increase in the odds of reporting GI symptoms. When broken down by specific issues, they found that those with ADHD were 97% more likely to experience constipation, 58% more likely to receive an IBS diagnosis, 52% more likely to have indigestion, over twice as likely to have diarrhea, and 88% more likely to have abdominal pain.
“The findings support paying attention to gastrointestinal health alongside ADHD care, looking beyond the narrow lens of an ‘attention deficit,’” says co-author Hugo Cannon, M.B.Ch.B.
What might be behind this link?
While the researchers cite several possibilities in their review, Blake cautions that it can’t necessarily prove that ADHD causes these GI symptoms, as some potential contributing factors include things like medication, other health conditions, or differences in daily routines.
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Behavioral symptoms
It’s possible that some of the symptoms of ADHD itself may contribute to problems with the gut. “For some people with ADHD, difficulties with planning and routines (like hyperfocus and executive dysfunction), or sensory preferences around food (like sensitivities to tastes, textures and smells), may influence what they eat and when. Dietary patterns could, in turn, affect bowel function and the microorganisms living in the gut,” Cannon explains.
However, he adds, “It should be noted that experiences vary between individuals, and not everyone with ADHD has the same eating patterns or difficulties.”
The gut-brain axis
Scientists are just beginning to understand how the gut and the brain are linked, and how one might affect the other; it’s possible that this connection may have something to do with the increased gastrointestinal symptoms seen in those with ADHD.
“The gut-brain axis involves nerves, including the vagus nerve, as well as hormones and immune signals. Microorganisms living in the gut can also interact with these pathways,” Blake says. “These interactive factors provide a plausible framework for investigating why gut symptoms and ADHD may occur together.”
Medication side effects
Finally, there’s the treatment of ADHD itself: People are often prescribed stimulants, many of which are known to cause gastrointestinal side effects.
What’s the takeaway?
Blake urges ADHD patients with gastrointestinal symptoms to discuss their problems with a healthcare provider, and cautions against “minimizing them or assuming they are simply part of ADHD.”
“Explain when the symptoms started, how they affect your daily life, and whether they changed after starting or adjusting medication. Gut symptoms can have several causes and deserve assessment in their own right,” she says. “If you have concerns about potential side effects of medication, discuss these with your healthcare provider. If managing meals or other daily routines is difficult, ask for support that fits your circumstances.”
“The aim should be manageable changes and appropriate care, without any blame or pressure to do everything perfectly,” Cannon adds. “Above all, be kind to yourself.”
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