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• A new study indicates there may be an association between attention deficit hyperactivity disorder (ADHD) and irritable bowel syndrome (IBS).
• Researchers say an altered gut microbiome may be one of the main factors for this connection.
• Further study is warranted, as one expert doesn’t believe there is a correlation between the two conditions.

In a new meta-analysis, scientists say they have established a “significant positive association” between attention deficit hyperactivity disorder (ADHD) and a higher risk of irritable bowel syndrome (IBS).

The researchers said an altered gut microbiome may be the “potential link that bridges the gap between ADHD and intestinal disorder.”

Their findings were published recently in the journal Scientific Reports.

The researchers said their analysis has significance in the daily lives of people with ADHD.

“IBS considerably affects quality of life in affected patients. Its presence in ADHD patients may further complicate the management of ADHD,” they wrote.

“Our results suggest that gut microbiome may explain the link between ADHD and IBS. Our finding of the positive association between ADHD and IBS suggests that clinicians should be aware of gastrointestinal symptoms in children and adults with ADHD,” they added.

The researchers noted there were several limitations to their analysis. They said that nearly half of the studies they examined were from Asia and only two studies included people of all ages.

One expert not involved in the study is highly critical of the research.

“I am highly critical of the study design, findings, and conclusions. The studies included into this meta-analysis are very heterogenous in terms of age, geographical region, study size, study design and probably in terms of diagnostic criteria used for IBS and ADHD,” said Emeran Mayer, MD, a professor of psychology medicine at the University of California Los Angeles and the director of the UCLA Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress.

“It is also highly likely that different diagnostic criteria were used for some of the IBS studies. Previous well-designed studies have shown no correlation between IBS and ADHD,” Mayer told Healthline.

Are IBS and ADHD linked?

To reach their conclusions, the researchers analyzed 11 past studies with 3.8 million individuals, including about 175,000 people with ADHD.

The 11 studies that were examined were all published within the past 25 years.

The researchers reported that the risk of IBS in people with ADHD was 1.63 times greater than in people who don’t have ADHD.

They added their research did not demonstrate an association between ADHD and other intestinal disorders.

The scientists noted that an altered gut microbiome has been implicated in a variety of neuropsychiatric disorders, including Parkinson’s disease, multiple sclerosis, and Alzheimer’s disease.

They added that children with ADHD tend to have more gastrointestinal issues, such as constipation and flatulence, than children without the condition.

They said these past studies have indicated that there is a connection between the gut-brain axis and ADHD.

Mayer isn’t convinced.

“The study is purely correlational and does not provide any evidence for a causal relationship between ADHD and IBS, or between gut microbiome and ADHD prevalence,” he said.

“On the other hand, given the high comorbidity of ADHD with other psychiatric disorders, including anxiety, and the high comorbidity of IBS with anxiety and depression, a correlation between IBS and ADHD is likely. IBS is a disorder of altered gut-brain interactions characterized by higher anxiety levels. Consistent alteration in the gut microbiome in IBS patients has not been reported.”

Max Wiznitzer, MD, pediatric neurologist at Rainbow Babies & Children’s Hospital, professor of pediatrics and neurology at Case Western Reserve University in Cleveland, and co-chair of the Professional Advisory Board at the Children and Adults with Attention Deficit Hyperactive Disorder (CHADD), said there are other better explanations for the association between ADHD and IBS. Wiznitzer wasn’t involved in the study.

“It is likely due to comorbid anxiety and/or depression,” Wiznitzer told Healthline.

“With the failure [of the researchers] to recognize or comment on the likely association with comorbid depression or anxiety by Ng et al in the Scientific Reports, the value of their conclusions is questionable (i.e., it is likely that the comorbid condition and not the ADHD is the reason for the association). Furthermore, they focus so much on gut microbiota that they overlook other potential reasons,” he noted.

What to know about ADHD

Attention-deficit hyperactivity disorder is described as a mental health condition that can cause impulsive behaviors.

Symptoms of ADHD include:

• difficulty focusing on a task
• being easily distracted
• unable to sit still for an extended period time
• interrupting people while they are talking

The American Psychiatric Association lists three different types of ADHD. They are:

• predominantly inattentive
• predominantly hyperactivity-impulsive
• a combination of both types

Scientists are still uncertain of the underlying cause of ADHD, although they believe genetics may be involved.

The researchers in the current study note that ADHD has been linked to a wide range of consequences for individuals.

These included an increased risk of smoking, substance-related disorders, sexual risk-taking behavior, greater driving risk, and suicidal behavior. They added that the chronic condition also poses a significant economic burden on families and society.

The researchers noted that ADHD can co-occur with other neuropsychiatric conditions such as autism spectrum disorder and bipolar disorder.

ADHD is generally diagnosed in children, although the condition can be present in adults. The condition is more prevalent in boys than in girls.

Treatments for ADHD include behavioral therapy and medication. A balanced diet, regular exercise, adequate sleep, and limiting screen time on phones, computers, and television are also recommended.

Mayer said there are therapies that can be beneficial.

“There is a number of behavioral techniques that have been used successfully in patients with ADHD. Similar cognitive behavioral techniques have been shown to benefit patients with IBS,” he said.

What to know about IBS

Irritable bowel syndrome is a group of intestinal symptoms that can include abdominal cramping, bloating, gas, diarrhea, and constipation.

The condition is more common in women than in men. It also tends to affect younger adults more often than older adults.

The symptoms are mild in some people but can be serious enough in other people to disrupt their daily lives.

The exact cause of IBS is not known, although an oversensitive colon and immune system difficulties are potential factors.

Triggers for IBS can include stress and anxiety. Some foods can also trigger IBS. They include:

• beans
• onions
• fruits
• certain dairy products
• certain carbohydrate-rich products

There are ways to help relieve IBS symptoms. These include:

• regular exercise
• limiting consumption of caffeinated beverages
• minimizing stress
• taking probiotics
• quitting smoking

Some nutritionists recommend that people with IBS adhere to a low FODMAP diet, an eating plan that focuses on avoiding certain carbohydrates.

“I recommend a multi-component treatment plan including personalized dietary recommendations, behavioral techniques, including self-relaxation techniques, mindfulness-based stress reduction, and cognitive behavioral therapy,” said Mayer.

“In more refractory cases, centrally acting medications like low dose tricyclic antidepressants. In patients with severe psychiatric comorbidity (anxiety or depression, less than 10% of all patients), I prescribed SSRIs,” he added.

Wiznitzer shared some simple advice for people with IBS. “Manage the anxiety and depression, and the IBS should improve,” he said.