Exploring the ADHD-Gut Connection: New Research Insights and Implications

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I started Reset ADHD in July of 2018 and began regularly blogging in the beginning of August of that year. In a blog post dated August 27, 2018, I wrote, “I hope more research is done in this area so that the relationship between ADHD and the gastrointestinal system is fully explored.” I had just gone through some diagnoses of stomach issues thanks to a visit to the Mayo Clinic in Rochester, Minnesota, and I was curious about the connection between stomach issues and ADHD. Since that time, more research has been done, and I have received another stomach-related diagnosis (gastroparesis). This has me thinking about the ADHD-stomach connection again. So, after doing some googling, I have discovered there have been several studies done on ADHD and stomach issues in the time since I last wrote about this topic.

Increased GI Issues

An Israeli study (Kedem et al (2020)) found that ADHD was associated with an increased rate of functional GI issues (e.g. IBS, constipation, and dyspepsia) but not somatic immune-mediated GI conditions, such as IBD and celiac disease. Moreover, this same study found “the ADHD group had a significantly increased rate of primary care visits for GI symptoms, referrals to GI specialists, and recurrent GI symptoms than the control group, pointing to the high burden of GI morbidity in individuals with ADHD on healthcare resources.”

Different Gut Ecosystem

The other area where research has expanded is the area of determining what is living in the guts of those with ADHD. You are probably aware that we have organisms living in our guts that can aid our gastrointestinal health or can cause problems, but what you may not have known is what a different make up of organisms can mean.

Studies are beginning to look into the gut composition of those with ADHD. Richarte et al (2021) “found evidence that ADHD subjects exhibit differences in the relative abundance of several microbial taxa.” Another study, done by Wang et al (2023), found that “the ADHD group displayed a significantly higher abundance of Ascomycota and a significantly lower abundance of Basidiomycota than the healthy control group. At the genus level, the abundance of Candida (especially Candida albicans) was significantly increased in ADHD patients compared to the healthy controls.” Stiernborg et al (2023) also found “further evidence to support a significant difference in the fecal microbiome composition in adult ADHD patients compared to adult controls.” The bottom line to these three studies is that the composition of the organisms living in the guts of those with ADHD are different than in those who do not have ADHD.

Does Medication Enter the Picture?

The Stiernborg study also reported that their “findings suggest a novel association between psychostimulant medication in children with ADHD and changes in fecal enzyme and strain bacterial diversity, and a lower abundance of bacterial genes encoding an enzyme in vitamin B12 synthesis.” This differs from my conclusions in my 2018 blog post. I said there was no evidence that gastrointestinal issues stem from medication side effects. However, they may play a role. It is possible but far from proven.

What Does All This Mean?

So, there are studies coming out about the gut and ADHD, but what do they mean? It is a fair question. Researchers try to describe their findings factually and without too much speculation. However, it is becoming abundantly clear that ADHD is associated with gastrointestinal distress and a different gut ecosystem. A 2018 study by Ming et al hypothesized, “Although more studies are needed to elucidate exact mechanisms and causality, we propose that an altered microbiome, gastrointestinal symptoms, and immune dysregulation may be associated with the ADHD phenotypes.” While all of these studies are illuminating, they say very little. For example, Sukmajaya et al (2021) sum up their study by saying, “Forty-nine bacterial taxa were found, yet none of them can explain the precise relationship between ADHD and the gut microbiota.” So, we are learning that the ADHD gut is different, but we are not really learning what that means. What is the relationship between the two? And is that relationship a causal relationship? In short, we do not know.

If you are like me, you know that more research is needed and is desired. I encourage researchers to keep probing the depths of the unknown surrounding ADHD gut health. There is more to learn, and the exact implications could change the way we go about treating ADHD.