Not Chaos. Not Character. Microbiome.

THE MICROBIOME SIGNATURE IN AUTISM AND ADHD IS NOT RANDOM

When families first hear the phrase gut microbiome they picture something vague. Something abstract. Something that might matter but is hard to pin down. Yet when we test children with autism, PANDAS, PANS and ADHD a clear pattern emerges.

A new study from 2025 confirms what we see in clinic every day. The microbiome changes in autism and ADHD are not small. They are measurable shifts in the gut ecosystem that affect immune activity, energy regulation, appetite hormones and behaviour.

The children in the study ranged from young boys with autism to nine and ten year olds with ADHD and adolescent girls with anorexia. All newly diagnosed. No probiotics. No antibiotics. No omega 3. No psychiatric medication. No extra noise in the data.

Even at these early ages the pattern was already fully established.

THE THREE DIAGNOSIS. THE SAME MICROBIOME DISTORTION

Autism
Boys around four to five years of age. Significantly lower microbial diversity. Higher Bacteroidetes. Lower Actinobacteria. Reduced Bifidobacterium. Increased Escherichia Shigella. Reduced Ruminococcus. The Bacteroidetes to Firmicutes ratio more than doubled. A gut under pressure.

ADHD
Children around nine to ten years of age. Again reduced microbial diversity. Lower Firmicutes. Lower Faecalibacterium. Higher Desulfobacterota. Higher Escherichia Shigella. The same skewed Bacteroidetes to Firmicutes ratio. A pattern strongly linked with inflammatory signalling.

Anorexia
Adolescent girls around fifteen years of age. Reduced Firmicutes. Reduced Bifidobacterium. Reduced Faecalibacterium. Higher Proteobacteria. Higher Cyanobacteria. Higher Verrucomicrobiota. Higher Desulfobacterota. The same dysbiosis signature in a different clinical picture.

Different diagnoses. Different ages. Different symptoms. The same foundational disruption in the gut ecosystem.

THE CONSISTENT MARKERS THAT MATTER

Low Bifidobacterium
Seen across autism, ADHD and anorexia. Bifidobacterium supports butyrate production, GABA metabolism and gut barrier integrity. When it drops, regulation drops. Children lose resilience.

Low Faecalibacterium
Particularly clear in ADHD and anorexia. Faecalibacterium is one of the core anti inflammatory organisms in the human gut. When it falls, inflammatory tone rises and behaviour is easier to tip.

High Escherichia Shigella
Elevated in autism and ADHD. This group produces endotoxins that activate the immune system inside the brain. The result is sensory instability, emotional swings and a nervous system that feels as if it is under constant threat.

High Bacteroidetes to Firmicutes ratio
Present in every diagnostic group. It is a recognised marker of metabolic strain and microbial imbalance. The gut is using more energy to keep basic functions going. There is less reserve left for behaviour, learning and recovery.

High Desulfobacterota
Raised in ADHD and anorexia and trending upwards in autism. These sulphur reducing bacteria are strongly associated with inflammatory disruption and toxic sulphur metabolites.

Parents describe their children as edgy, volatile and easily overwhelmed. The biology matches the description.

THE MISSING PIECE MOST CLINICIANS OVERLOOK: SATIETY HORMONES

Satiety hormones are not about willpower. They are safety signals. They tell the brain whether the body is fed, safe and stable. When these signals drop, behaviour becomes unpredictable.

In this study:

ADHD
Peptide YY was lower. PYY helps stabilise appetite and supports calm attention. Low levels sit well with impulsive eating, constant grazing and emotional swings.

Anorexia
Leptin, ghrelin and PYY were all lower. The signalling system that regulates hunger and nervous system energy had been turned down. The body behaved as if fuel and safety were both uncertain.

Autism
Average levels of satiety hormones did not shift as dramatically but they tracked closely with specific bacteria such as Bacteroides and Escherichia Shigella. Even without obvious hormone changes the gut was still steering the signals.

The message is clear. Microbial imbalance destabilises hormonal signalling. Hormonal instability destabilises behaviour.

THIS IS NOT RANDOM. IT IS A BIOLOGICAL NETWORK

Inflammation
Low diversity and higher Proteobacteria push the immune system towards an inflamed state. Children lose their buffer. Small stresses feel large.

Energy regulation
Low Faecalibacterium and low Firmicutes reduce short chain fatty acid production. Mitochondria lose one of their cleanest fuel sources. Fatigue and irritability rise.

Gut brain signalling
Escherichia Shigella increases vagus nerve alerts and immune signalling from gut to brain. The nervous system behaves as if danger is close even when the environment is calm.

Satiety tone
Low PYY and altered ghrelin and leptin unsettle internal rhythm. Children feel wired, hungry, flat or anxious in ways they cannot describe.

Parents often say their child lives with low reserve. This is what low reserve looks like biochemically.

WHAT THIS MEANS FOR CLINICAL PRACTICE

This study backs up what many families already sense. Behaviour is not only neurological. It is microbial, inflammatory and metabolic.

The practical focus:

Rebuild Bifidobacterium
Use targeted prebiotics, gentle fermentable fibre and polyphenol rich foods. Many sensitive children do best with very slow, stepwise changes.

Restore Faecalibacterium and butyrate pathways
Support butyrate production with resistant starch, cooked and cooled roots, and anti inflammatory fats. Reduce ultra processed foods that disrupt these pathways.

Reduce Escherichia Shigella pressure
Pull back on processed carbohydrates. Support mucosal immunity. Use targeted botanicals if needed, always in the context of a wider plan.

Lower Desulfobacterota activity
Reduce sulphur heavy foods for a period if appropriate. Support detoxification, bile flow and gut lining repair.

Stabilise satiety signalling
Calm gut inflammation first. As the gut steadies, leptin, ghrelin and PYY often move back towards a healthier pattern without needing to chase each hormone directly.

TESTING IS THE TURNING POINT

Testing is not optional. It is the point at which confusion turns into clarity.

Parents come in thinking their child is unpredictable. The data shows the child is running on a gut ecosystem that cannot hold stability. When we analyse the microbiome we are not looking for random numbers. We are looking for the biological reasons a child struggles with mood, attention, sleep, sensory load and resilience.

The patterns are measurable. The 2025 study shows that even in children as young as four the microbiome has already shifted in ways that affect inflammation, energy and gut brain signalling. When we run advanced stool testing we see the same thing. Low Bifidobacterium. Low Faecalibacterium. High Escherichia Shigella. Distorted Bacteroidetes to Firmicutes ratios. These shifts explain why a child reacts before they can think. They explain why behaviour feels bigger than the situation.

Testing removes guesswork. It shows which pathways are under strain and which can recover. It shows whether your child is struggling because the gut is inflamed, whether the microbiome has collapsed, whether butyrate is missing, whether toxins are rising or whether satiety hormones have been pushed off balance. Each result shows where stability is leaking.

Most importantly the data tells parents something they rarely hear. Their child is not broken. Their child is running a biology that can change.

When we rebuild the microbiome behaviour improves. Mood evens out. Focus strengthens. Sleep steadies. Children reconnect with themselves and with others. The difference can be profound.

This is why we test. When the gut shifts the child shifts.

WHAT PARENTS NEED TO HEAR

Even four year old children in the autism group already showed measurable microbiome disruption.

Children with ADHD had microbiomes that looked more inflamed than many adults with long term illness.

Teenage girls with anorexia showed the same missing beneficial bacteria found in young autistic boys.

This is not a moral failing or a character flaw. It is biology.

When the gut is unstable the brain becomes reactive. When the microbiome steadies behaviour becomes more predictable, learning becomes easier and daily life becomes less of a battle.

The study confirms what your child has been showing you all along. Their behaviour is a signal, not a verdict.

IMPORTANT

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Always consult with medical doctors or qualified functional medicine practitioners before introducing any new supplement, test or intervention.

Concerned about your child’s health? We are happy to talk.

References

Soltysova, M., Tomova, A., Paulinyova, M., Lakatosova, S., Trebaticka, J., Ostatnikova, D., 2025. Gut microbiota in children and adolescents with autism, ADHD and anorexia nervosa, and its link to the levels of satiety hormones. Neuroscience, 585, 394–407.
PubMed

Lewandowska Pietruszka, Z., Figlerowicz, M., Mazur Melewska, K., 2023. Microbiota in autism spectrum disorder: a systematic review. International Journal of Molecular Sciences, 24(23), 16660.
MDPI

Hughes, H. K., Rose, D., Ashwood, P., 2018. The gut microbiota and dysbiosis in autism spectrum disorders. Current Neurology and Neuroscience Reports, 18(11), 81.
PubMed

Iglesias Vázquez, L., Van Ginkel, R., Arija, V., Canals, J., 2020. Composition of gut microbiota in children with autism spectrum disorder: a systematic review and meta analysis. Nutrients, 12(3), 792.
MDPI

Kang, D. W., Adams, J. B., Coleman, D. M., Pollard, E. L., Maldonado, J., McDonough Means, S., et al., 2019. Long term benefit of microbiota transfer therapy on autism symptoms and gut microbiota. Scientific Reports, 9, 5821.
Nature

Wang, Q., Luo, Z., He, F., Peng, K., 2023. Microbiota–gut–brain axis and neurodevelopmental disorders. Protein & Cell, 14(10), 762–800.
Oxford Academic