A new review and meta-analysis conducted by a research team from the Warwick Medical School, University of Warwick, in Coventry, United Kingdom, confirms a striking association.
The review, which looked at data from 23 studies totaling more than 1.9 million participants between them, found a strong link between attention deficit hyperactivity disorder (ADHD) and the experience of a varied array of gastrointestinal symptoms and disorders.
People with ADHD had a heightened likelihood of developing “every [gastrointestinal] symptom investigated,” the authors write in the paper, which appears in the Journal of Attention Disorders.
Speaking to Medical News Today, co-lead review author Sarah Blake, a medical student at Warwick Medical School, explained that her and her colleagues’ interest in this topic stemmed both from intriguing clues provided by previous research, and from some of the researchers’ own experience.
“Hugo [co-lead author Hugo Cannon, MBBS] and I came to this topic from different perspectives,” Blake told us. “My interest grew from research I encountered during my undergraduate degree, while Hugo’s interest was additionally shaped by personal experience.”
“Previous research had suggested connections between ADHD and gastrointestinal problems. We wanted to bring together the evidence on individual gut symptoms and conditions to understand which specifically were more common in people with ADHD and how consistent the findings were across studies. We hoped this would help clinicians recognise coexiting problems and help researchers identify questions that future studies need to answer.”
— Sarah Blake
The systematic review looked at studies conducted in 11 countries, including the United States, South Korea, Sweden, Greece, India, and Iran.
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The populations covered in the studies included participants of all ages, from ages 2 to 65.
“Overall, ADHD diagnosis was associated with a statistically significant 48% increase in [gastrointestinal] symptom odds compared to the neurotypical population,” the review found.
The odds of experiencing specific gastrointestinal issues were even higher among ADHDers:
While the link between ADHD and gastrointestinal problems is strikingly strong, based on the available data, it remains unclear why these neurodivergent populations face such high odds of issues like IBS, indigestion, and abdominal pain.
Speaking to MNT, Blake hypothesized that the gut-brain axis may hold the key to answering this particular research question.
“Research into communication between the gut and brain (the gut-brain axis), and alterations in the gut microbiome, suggested this review may be worthwhile,” she told us.
Blake even suggested that the increase in gut problems may be a common experience across different neurodivergent populations.
“There have also been well-described findings around the increase in experienced [gastrointestinal] symptoms in autism spectrum disorders compared to those without,” she pointed out, adding, however, that the research team preferred to keep their review targeted and specific for the time being, to avoid confusion.
Sylvia Baker, MRCpsych, consultant psychiatrist at Re:Cognition Health, who was not involved in the recent review, explained that the link between ADHD and gut problems is likely to have a very complex explanation.
“The relationship between ADHD and gastrointestinal symptoms is likely to be complex rather than having one single explanation. We know that ADHD can affect much more than attention and concentration, with difficulties around emotional regulation, impulsivity, routines, eating patterns, and sleep all potentially playing a role in physical health,” Baker said.
“One possibility,” she suggested, “is that some of the behavioral characteristics associated with ADHD can directly influence the gut.”
“People with ADHD may be more likely to skip meals, eat irregularly, eat quickly or have periods of impulsive or binge eating. Some may also have strong sensory preferences around food texture, taste or smell, which can lead to a narrower diet and, in some cases, lower fiber intake. All of these factors are able to affect bowel function and digestive symptoms.”
— Sylvia Baker, MRCpsych
“Stress and emotional dysregulation may be another important piece of the puzzle,” Baker continued. “The gut and brain are in constant two-way communication, and increased stress can influence gut motility and visceral sensitivity – essentially, how strongly we experience sensations such as bloating or abdominal discomfort.”
“This may be particularly relevant to functional gastrointestinal conditions such as IBS,” she noted.
Like Blake, Baker said that the gut-brain axis may be involved, citing studies that “identified differences in gut microbial composition in people with ADHD.”
Finally, she also raised the possibility that medication may affect gastrointestinal function in some cases.
“Stimulant medications can cause gastrointestinal side effects in some people, including reduced appetite, abdominal pain, nausea, and in some cases, constipation,” Baker explained, cautioning that “this is one reason it is important not to assume that every gastrointestinal symptom in someone with ADHD is part of the condition itself.”
Blake told MNT that ever since the review was published, she and her colleagues have been hearing from parents, concerned about how to obtain support for their children with ADHD who experience gastrointestinal issues.
“Their experiences reinforce why this question is important, although our research cannot explain any individual child’s symptoms,” said Blake, emphasizing that the recent review “supports greater awareness” of the link between ADHD and gut problems.
“We hope the findings encourage clinicians to ask about persistent or troublesome gut symptoms when caring for people with ADHD and consider their impact on everyday life,” she told us.
She also stressed that “those symptoms deserve assessment in their own right and should not automatically be attributed to ADHD or its medication, adding that “we […] need research to distinguish medication effects from other possible contributors and establish which approaches improve care.”
According to Baker, the first step that individuals with ADHD can take in mitigating their gastrointestinal risks “is simply to recognise the connection and not dismiss persistent digestive symptoms as unrelated.”
“If someone with ADHD is regularly experiencing constipation, diarrhea, abdominal pain, bloating or changes in bowel habits, it is worth discussing this with their [family doctor] rather than simply putting it down to their ADHD,” she advised.
As for actionable strategies, Baker said:
“In practical terms, building consistency can help. Regular meals, adequate fluid intake, sufficient dietary fiber and regular physical activity are all sensible foundations for good bowel health. For someone with ADHD, however, knowing what to do and being able to do it consistently are not always the same thing. Setting reminders for meals and hydration, keeping simple nutritious foods readily available and creating predictable routines can make these changes much more achievable.”
“It is also worth looking at the wider picture. Poor sleep and high levels of stress can affect gastrointestinal function, therefore, addressing sleep and stress management may help alongside dietary and medical measures,” she added.
Moreover, Baker reminded us that medication can affect the gastrointestinal system, and she advised that “if symptoms started or became noticeably worse after beginning or changing ADHD medication, that should be discussed with the prescribing clinician.”
Lastly, she “cautioned against adopting restrictive diets or taking multiple supplements” based on anecdotal evidence and without consulting a specialist doctor beforehand.
Going forward, Baker said she would like to see studies focusing not just on the “what” but on the “why,” looking for the mechanisms that might explain the link between ADHD and gut problems.
“We need good-quality longitudinal studies that follow people over time,” she told MNT. “This would help establish whether gastrointestinal symptoms tend to appear before ADHD is diagnosed, develop alongside ADHD, or emerge following treatment or particular lifestyle changes.”
“I would particularly like to see studies that examine the gut microbiome alongside detailed clinical information about ADHD symptoms, diet, medication, sleep, stress, and gastrointestinal symptoms,” added Baker.
“At present, it is tempting to look at microbiome differences and assume they are causal, but we simply do not have enough evidence to make that leap,” she cautioned.
Ultimately, Baker called for “research that looks at whether treating gastrointestinal problems has any meaningful effect on quality of life or ADHD symptoms, and vice versa.”
“That is where this research becomes clinically useful. If we can identify specific mechanisms, we may be able to develop more personalised approaches to managing both ADHD and gastrointestinal health,” she concluded.
