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Gut, Autism, and ADHD

Intriguing links between the microbiota at birth and later diagnosis of illness.

Flickr Creative Commons
Source: Flickr Creative Commons

In the United States, nearly one-third of children are born via c-section. Usually mothers don’t have much of a choice about the matter, so don’t pat yourself on the back and be judgmental of c-sections if you or your kids made it out the good old-fashioned way.

However, this relatively “sterile” form of delivery compared to passing through the vagina does result in a marked difference in the gut of children born via c-section vs. vaginally. Babies pick up commensal bacteria from moms during a natural delivery that don’t make it to c-section kids, who tend to get colonized with the skin flora of the folks handling the baby first.*

Since there is so much information now about how the gut microbiota impacts human health, are there health differences between babies born by c-section or vaginally due to the change in microbiota?

There are certainly differences in the health of c-section vs. vaginally delivered kids. Those born by c-section have higher rates of asthma, allergies, gastrointestinal problems, and diabetes. In addition there are small but significant increases in the risk of psychiatric disorders, such as bipolar disorder, autism spectrum disorders, and ADHD.

Since the microbiota influences immunity and inflammation, and many of these disorders are known to be autoimmune or have inflammatory components, it would make sense that a changed microbiota due to c-section delivery could be responsible for some of these differences. However, that’s a hard thing to prove. After all, many babies are born by c-section because there is fetal distress or maternal health problems, making the cohort of c-section kids different in many ways compared to vaginally delivered babies. There are also many, many people with allergies, asthma, and/or psychiatric disorders who were born vaginally.

It’s also important to realize that ADHD and autistic spectrum disorders are highly inherited, so a change in gut bacteria alone is only a part of many risk factors that could lead to these disorders presenting in kids. We do know that the gut microbiota of kids with autism spectrum are different than kids without, which may be due to differences in diet or even antibiotic exposure in childhood.

Researchers in Finland did a remarkable long term experiment to try to shed some light on the question of autistic spectrum, ADHD, and the microbiota. They treated seventy-five babies between 0-6 months with a probiotic (Lactobacillus rhamnosus) or placebo, then followed the children for 13 years. In addition, they took some measures of the microbiota of the children. These kids were randomly selected, so about 80% were born vaginally.

At the end of the study, 0% of the probiotic group had a diagnosis of ADHD or autism spectrum disorders, whereas 17% of the kids in the placebo group did have a diagnosis. Despite the small size of the study, that number was statistically significant. They found that kids with the diagnosis of autism spectrum or ADHD had lower levels of Bifidobacteria species as babies than kids without a diagnosis. (Apologies to microbiota experts for a gross generalization here, but Lactobacillus and Bifidobacteria seem to work together, so supplementing with certain kinds of Lactobacillus species seems to increase the populations of Bifidobacteria in folks.)

The diagnosis of ADHD or autism in 6 placebo kids (all male, by the way) among a group of 75 children is fascinating, but by no means definitive. The microbiota is affected by all sorts of factors: diet, stress, and prebiotics (certain fibers that serve as food for the gut microbiota). There are many research tracts to follow regarding what probiotic or prebiotic to even study, what changes are wrought in the gut and immune system, and what kind of dose or modifications are optimal.

Researchers are studying the effects of swabbing c-section infants with vaginal flora on delivery. If it turns out to be low risk and even modestly effective for establishing a robust microbiota in c-section babies, there may be extensive population benefits in all sorts of measures of health. In my view, the microbiota at birth have to be supported throughout childhood with a good whole foods diet to keep the little beasties in the gut as happy as can be.

*Breast milk also has major differences in prebiotics and probiotics vs. formula.

Image credit: flickr creative commons

Copyright Emily Deans MD

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