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ADHD and Gut Health are More Connected Than You Think

Written by Dr. Michael Ruscio, DC on September 25, 2023

Written by Dr. Michael Ruscio, DC on September 25, 2023 — Reviewed by Kellie Blake

• ADHD Overview|
• Not Just Neurotransmitters: The Microbiome and ADHD|
• The Gut-Brain Axis and ADHD|
• Does Gut Dysbiosis Cause ADHD?|
• Can Gut Health Treatments Improve ADHD?|
• Heal Your Gut to Balance Your Brain|

For decades, attention deficit hyperactivity disorder (ADHD, formerly known as attention deficit disorder, ADD) has been labeled primarily as a disorder of the brain, possibly extending to the central nervous system. However, it’s becoming more and more clear that the gut — especially the gut microbiome — has a say in many different neurological and psychiatric disorders, including ADHD. 

ADHD may look like difficulty paying attention and maintaining concentration, disorganization, poor emotional regulation, and forgetfulness, among other symptoms. All of these issues can be influenced by a dysregulated gut. 

So that begs the question about ADHD and gut health: can healing your gut improve or even resolve ADHD symptoms? Let’s see what the research has to say and investigate possible treatments, including diet, probiotics, and antimicrobials. 

ADHD Overview

Before we dig into the research on gut health and ADHD, let’s do a quick overview of the basics. Attention deficit hyperactivity disorder is considered a neurodevelopmental disorder or neuropsychiatric disorder, usually diagnosed in childhood before the age of 12. However, adults may be diagnosed with the condition too, often after having been dismissed or unacknowledged in childhood when it first manifested. This is especially true for girls, who are more likely to have the inattentive subtype rather than hyperactive, and so may go relatively unnoticed until much later in life. 

The most common presentations include 1: 

• Poor attention and concentration
• Constant need to move or fidget
• Emotional dysregulation
• Impulsivity
• Disorganization
• Difficulty making decisions
• Trouble finishing tasks
• Forgetfulness
• Frequently losing things 

ADHD has three different subtypes: predominantly hyperactive/impulsive, predominantly inattentive, and combined hyperactive/impulsive and inattentive 1. Among all ADHD patients, about 8% are hyperactive/impulsive, about 18% fall under the inattentive subtype, and about 70% demonstrate the combined subtype 1.

ADHD is thought to arise from a combination of genes (it’s very common in siblings) and triggers in the environment — including possible viral infections, smoking and/or drinking during pregnancy, and nutritional deficiencies during pregnancy and after birth — affecting certain receptors in the brain 1. According to the CDC, about 6 million (almost 10% of) children in the US received an ADHD diagnosis from 2016–2019 2. 

It has also been assumed for many years that most children with ADHD will “outgrow” the condition as they grow into adulthood. While some symptoms, like hyperactivity and inability to sit still, may diminish over time, it’s likely that certain ADHD symptoms will persist into adulthood, such as a tendency toward disorganization, impulsive behavior, inattention, and forgetfulness. Adults are much more likely to “mask” these symptoms to be accepted socially, while children have not learned such behaviors yet. 

The first-line conventional treatment for ADHD in children and adults is stimulant medications, which can be very effective and safe when given properly, however perhaps not sustainable. They are also at a high risk for side effects, including weight loss, suppressed appetite, irritability, and more 1. Non-stimulant ADHD medications are also available if stimulants are not an option, but they tend not to be as effective as stimulants 1. Well-researched non-pharmacological treatments include psychosocial therapies like psychoeducation for the family and patient and cognitive behavioral therapy (CBT) 1.

With that said, let’s move on to ADHD and gut health. 

Not Just Neurotransmitters: How the Microbiome Affects ADHD

As with anxiety and depression, the predominant thought on what causes ADHD is an imbalance of neurotransmitters (such as dopamine, norepinephrine, and serotonin) in the brain. And just like anxiety and depression, that isn’t the whole story. 

While more research needs to be done, there seems to be at least a connection between a disordered gut and ADHD, even if we can’t definitively say that one causes the other. For example, research showing gut bacteria differences in children with ADHD challenges the idea that the condition is solely related to neurotransmitters 3. 

Another study showed that people of all ages with ADHD appeared to have a distinct gut bacteria profile that overlapped with conditions like anorexia and bipolar disorder, suggesting probiotics and a healthy diet could aid in treatment (by correcting the microbiome) 4. Indeed, gut dysbiosis may play a role in ADHD in kids and adults and could be a useful target for therapy.

Along these lines, another recent study showed that fungal dysbiosis in the gut, specifically levels of Candida albicans, were “significantly increased in ADHD patients compared to the healthy controls” 5. This suggests that curbing Candida growth may improve symptoms of ADHD in certain individuals. 

Other studies show that taking antibiotics during pregnancy may be linked to a higher risk of ADHD in offspring (in both human clinical trials and lab studies on mice) 6 7, perhaps by impacting fetal development through the mother’s gut 7. The same risk of ADHD wasn’t found for infants who received antibiotics only out of the womb, in their first years of life 7. 

Gut conditions, such as celiac disease 8 and excess gut permeability, aka leaky gut 9, may also elevate ADHD risk. In fact, high levels of a leaky gut biomarker called zonulin appeared to correlate with more severe ADHD symptoms in children 9.

One way to imagine the impact of leaky gut on the brain looks something like this: 

Intestinal inflammation → increased permeability → bacterial metabolites (lipopolysaccharides, aka LPS) travel to the brain → cause neuroinflammation → mental health symptoms occur.

Clearly, there are many factors associated with the gut that may contribute to developing ADHD. But what about how the gut impacts the brain itself?

The Gut-Brain Axis and ADHD

While the gut is considered your “second brain” and has a nervous system of its own (another potential reason for its involvement in neurological disorders), the gut can also send messages to your actual brain to either perform optimally or cause mixed signals (and vice versa). This is called the gut-brain axis. 

One major player in the gut-brain axis is the vagus nerve, the long wandering nerve that connects the brain to the gastrointestinal system, among other essential organs, including the heart and lungs. Dysbiosis and inflammation in the gut can negatively impact the vagus nerve, which impairs communication with the brain and compounds inflammation. There isn’t much direct research on this connection, but it’s not illogical to assume that an inflamed gut causing an inflamed brain via the gut-brain axis could be contributing to ADHD symptoms 3. 

Does Gut Dysbiosis Cause ADHD?

Based on current research, we can say that gut dysbiosis may play a role in ADHD and could be a useful target for therapy 10. This could look like an imbalanced bacteria profile 4, fungal overgrowth 5, viral infections 1, and parasitic infections 11 12. These pathogens may cause immune system and nervous system dysregulation that could show up as ADHD and other brain-related symptoms. 

In fact, dysbiosis can cause intestinal inflammation, leading to leaky gut, food sensitivities, vagus nerve disruption, and neuroinflammation, as we discussed above. On another level, dysbiosis in the gut could also limit nutrient absorption which could contribute to ADHD symptoms. 

Can Gut Health Treatments Improve ADHD Symptoms?

Now that we know poor gut health may contribute to or cause ADHD, let’s see what we can do to improve it with gut health treatments.  

Diet

While there isn’t a specific diet tied to improving ADHD, we do have some broad research on healthy, whole food-based diets improving ADHD symptoms in kids and teens. Two large meta-analysis research reviews linked healthy diets (veggies, fruits, legumes, fish) to lower ADHD risk in kids and teens, whereas Western and junk food diets raised the risk 13 14. Another study suggested that certain synthetic food colorings might affect attention in kids with ADHD 15. 

Based on these studies, a good diet strategy for ADHD seems to be eating as many whole-food, antioxidant-rich, nutrient-rich foods as possible, and the least amount of processed foods possible. 

We also know that certain nutrients, including vitamin D and zinc, may help curb ADHD symptoms, which can be acquired through a healthy diet (and sun exposure in the case of vitamin D) 16 17. Multivitamin/multimineral supplements have also been shown to be helpful for children with ADHD when taken consistently, again showing that a wide range of nutrients found in a healthy diet are likely beneficial to counteract ADHD symptoms 18 19.

Plus, an anti-inflammatory diet can help restore the microbiome, regulate the vagus nerve, reduce neuroinflammation, decrease leaky gut, and help increase proper nutrient absorption from foods through the gut lining. So we can approach ADHD from multiple angles by implementing a healthy diet. 

If you’re looking for a little more guidance and parameters to follow, I recommend most of my patients start on the Paleo diet for optimal gut and brain health. You can find a full breakdown and recommendations on how to start Paleo here. 

Probiotics

Beyond a healthy diet, we do have some promising research on how probiotics (beneficial bacteria) may benefit brain function for those with ADHD. 

One RCT found that kids with ADHD who took synbiotics (prebiotic + probiotic supplements) had less ADHD-associated inflammation, in part because the synbiotics increased short-chain fatty acid production 20. 

Another RCT found that kids whose mothers took probiotics during pregnancy and then gave them probiotics for the first 6 months of life had a lower risk of developing ADHD than kids and their moms who took a placebo 21. 

Finally, a small nonrandomized trial showed that after kids and teens with ADHD took probiotics for 8 weeks, their clinical symptoms improved and their gut microbes changed 22.

If you want to try probiotics, I recommend a multi-species Lactobacillus and Bifidobacterium blend starting with at least 1-10 billion CFUs. Or you can check out our Probiotic Triple Therapy sticks, which combine all three types of probiotics (multi-species, soil-based, and S. boulardii) in one. We typically find in our clinic that even those who haven’t had success with other probiotics in the past respond well to our triple therapy approach. 

Short-Chain Fatty Acids

Interestingly, the bulk of research shows that omega-3 essential fatty acids don’t seem to improve outcomes of ADHD 23 24. However, short-chain fatty acids (SCFAs), like butyrate, may have some merit. A study of Korean elementary school students found that those with ADHD had significantly lower diversity in their gut microbiota and much lower concentrations of short-chain fatty acids acetate and butyrate than the control group 25. Similar low levels of SCFAs have also been found in adults with ADHD 26. 

While low SCFAs may not necessarily cause ADHD, it’s likely some kind of dysbiosis is leading to disrupted microorganisms in the gut, low SCFA levels such as butyrate, and ADHD symptoms. Besides optimizing the diet and consuming resistant starches, which your gut ferments to create butyrate, supplementing butyrate alongside probiotics may be a therapeutic option for ADHD. 

Antimicrobials

If gut infections are present, antimicrobials may also be used to help improve ADHD symptoms. Which antimicrobial you need will depend on the type of infection and individual tolerance. For example, oil of oregano is a powerful antimicrobial for just about any pathogen, but for some, it may be too strong. Or you may need a combination of antimicrobials such as berberine, artemisia, caprylic acid, and others. 

In this case, it’s probably a good idea to work with a healthcare practitioner who can help you determine what kind of dysbiosis is present in your gut and the best options to treat it. 

Heal Your Gut to Balance Your Brain

Whether poor gut health is a root cause for your ADHD symptoms or one factor of many, supporting your gut health can only bring benefits to your brain and overall mental health. You may be surprised by what even simple changes like following a Paleo diet or taking daily probiotics can make!

You can learn more about gut-healing diets, protocols for dysbiosis, probiotics, and much more for your overall health and wellness in my book Healthy Gut, Healthy You.

The Ruscio Institute has developed a range of high-quality formulations to help our patients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you.