Most people with ADHD have disturbed gut bugs
By naturopath Margaret Jasinska
Researchers are finding surprising connections between disruptions in gut health and ADHD. There is a 63% higher risk of irritable bowel syndrome in people with ADHD.
If you or your child have ADHD, you may experience digestive troubles, and it turns out that’s probably not a coincidence. A growing body of research is uncovering a real, biological link between attention-deficit hyperactivity disorder and certain gut problems. Scientists think the key to understanding this connection may lie in the trillions of microbes living in our digestive system.
What’s the connection between ADHD and gut problems?
People with ADHD are significantly more likely to experience certain digestive conditions. A major 2025 analysis combining data from 11 studies involving more than 175,000 people with ADHD and 3.6 million without found that people with ADHD have a higher chance of having irritable bowel syndrome, chronic constipation and indigestion.
Researchers believe ADHD and many gut disorders share common roots in the way the brain and gut communicate with each other (called the gut-brain axis).
Your gut and brain are in constant communication. The digestive system has its own extensive network of nerves, sometimes called the second brain. The gut sends signals to the brain via the vagus nerve, hormones, and the bloodstream. Disruptions in the gut can directly affect mood, focus, and behaviour, and vice versa.
The role of gut bugs
Your gut is home to a vast community of bacteria, fungi, and other microbes, collectively called the gut microbiome. In healthy people, this ecosystem is diverse and balanced. When that balance is disrupted (called dysbiosis), things can go wrong in any part of the body, including the brain.
Gut bacteria help produce neurotransmitters, that the brain uses for concentration, impulse control, and mood. When the gut microbiome is out of balance, these processes can be disrupted. Certain bacteria can also damage the gut’s protective lining and trigger inflammation (leaky gut), with effects that reach all the way to the brain.
In one 2024 study of children and adolescents with ADHD, researchers found that kids with ADHD had noticeably less diverse gut bacteria than children without ADHD, as well as lower levels of certain fatty acids important for brain function.
Does gut disruption in infancy predict ADHD later?
An interesting finding comes from a landmark international study published in 2024, which followed more than 16,000 children from birth. The researchers found that disruptions in the infant gut microbiome appeared before the children were diagnosed with ADHD or autism; sometimes years before. This suggests the gut disruption isn’t just a side effect of having ADHD; it may actually play a role in causing it.
Children who later developed ADHD consistently showed differences in their gut microbial makeup from birth. They also had higher levels of pro-inflammatory bacteria and lower levels of protective, anti-inflammatory bacteria.
According to lead researcher Dr Andrea Cassidy-Bushrow, “We know that antibiotic use, mode of delivery, and infant diet are all key determinants of a child’s early-life gut microbiome composition.”
Several early-life factors appear to influence both gut microbiome development and the risk of ADHD:
- Antibiotics. Both taken by the mother during pregnancy and given to the infant can disrupt the developing gut microbiome. Children with frequent early antibiotic exposure were more than twice as likely to develop neurodevelopmental disorders in some studies. Certain bacteria that overgrow after antibiotic use were found at higher levels in children who later developed ADHD.
- Mode of birth. Babies born vaginally are colonised with bacteria from the birth canal; those born by caesarean section miss this early microbial exposure, which can affect their microbiome long-term.
- Infant diet. Breastfeeding, in particular, helps establish a healthy and diverse gut ecosystem. A varied diet based on whole foods and low in sugar helps to establish healthy gut bugs.
- Environmental exposures, including maternal smoking, certain medications including paracetamol and environmental chemicals have also been linked to gut disruption and later ADHD or autism.
GABA is a key brain neurotransmitter that helps with impulse control and calm focus. People with ADHD and autism often have lower levels of GABA in the brain. This can create anxiety and poor sleep. Interestingly, certain bad gut bacteria consume GABA. Researchers have found that when these bacteria are overrepresented in the gut, GABA levels in the blood are lower.
The hope among researchers is that one day, specific bacterial patterns in a baby’s gut could flag neurodevelopmental risk long before any symptoms appear, allowing for earlier support and intervention. Some scientists believe that targeting gut health early could alter the course of ADHD development.
How can we help people with ADHD right now?
Medical practitioners treating people with ADHD should be alert to the possibility of underlying gut disorders. Irritable bowel syndrome, constipation and indigestion can usually be helped with diet changes, healing leaky gut and killing off bad gut bugs that have overgrown in the intestines.
A diet that is based on meat, seafood, poultry, eggs, vegetables and natural fats is usually best tolerated by most people. Grains, dairy products, sugar and high FODMAP foods often aggravate the gut and aggravate mental health symptoms.
BactoClear capsules contain the essential oils of clove, oregano and thyme, as well as the herbal extract berberine. They are helpful for abdominal bloating and symptoms of medically diagnosed irritable bowel syndrome.
An overgrowth of bad gut bugs will usually create a leaky gut. When the gut lining is excessively permeable, the immune cells living in the gut become chronically stimulated and over reactive. This raises inflammation right throughout the body, including the brain. Ultimate Gut Health powder contains specific ingredients designed to heal, soothe and repair a leaky gut.
For more information about healing your gut see the books Healing Autoimmune Disease and Healthy Bowel Healthy Body.
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