Microbiome Alterations by 12 Months and the Development of Behavioral Issues

One of the many subjects being studied that are of particular interest to me is the long-term effect of alterations to the early, developing microbiome.  There is little doubt at this point that at the very least, the bacterial microbiome, is a huge factor in the current epidemic of autism.  It likely plays a role in childhood asthma, ADHD, allergies, and many more illnesses.  As a first-hand witness to the effects of early antibiotics on behavior, I have followed this research very carefully for 25 years now.   Those first two years of life – especially so the first year – are critical in the establishment of normal, healthy microbiota.

A paper on how the gut microbiota develop during infancy, and how this may relate to future behavior issues, caught my eye a couple of weeks ago, and I finally had a chance to read it this week.[i]  There is not a lot of research on this topic yet, believe it or not.  Prior research had shown (in a cohort of 77 infants) an association between microbiome diversity and temperamental issues.  Another study noted an inverse association between bacterial diversity at 12 months of age and overall cognitive and language measures at 2 years old (i.e. the more diversity at 12 months, the lower the cognition and language scores at 2 years).  (This is interesting, as it’s the opposite of what you’d expect in an adult.  But as you know, from this blog post of a few weeks ago, what is healthy for someone at one age may not be at all healthy for them at another point in their life.  Of course, the results need to be confirmed in future testing.)

This study used an overall sample of 1074 infants, 201 of which had sufficient data to be included in the research.  Stool was collected at 1, 6 and 12 months of age, and infant behavior was analyzed using a couple of testing questionnaires.  At 2 year of age, 22 of the 201 babies were classified as cases with elevated behavioral problems.

The results show that in those with behavioral abnormalities, at 12 months Prevotella was detected only 4% of the time, whereas in those without behavioral issues, it was detected 44% of the time.  This is highly statistically significant.  This finding stood even when adjusted for other possible cofactors, like the baby’s sex, maternal smoking, household income, number of siblings, infant feeding practices, and so forth.  Not a surprise, the use of antibiotics between 9 and 12 months was associated with reduced Prevotella:  this was the “best predictor” of Prevotella absence.  (I have written about Prevotella many times on this blog.  We know it is more abundant in non-Western populations who eat much higher levels of fibers.  Generally speaking, it is regarded as a probiotic species.)

Antibiotic exposure prior to that 9-12 month period of time was not a predictor of lower Prevotella.  The authors hypothesize that this is because the microbiota have a chance to normalize, but exactly how diet and other environmental and internal factors affect reconstitution is unknown.  A lot more work needs to be done on how antibiotic use may be a factor in later developmental issues.

The authors conclude by stating that they have “…identified potential microbial targets for improving behavior, and factors which may affect them, such as antibiotic use.  This study adds support to evidence that the human infant gut microbiota may have long-term neurodevelopmental consequences, conferring protection or vulnerability to behavioral and mental health outcomes in later life.”

I often wonder what our lives would have been like had Alex not been given antibiotics at birth for 5 days and then again, for 2 weeks just before his 1st birthday.   While I try not to go there, it’s really hard sometimes, as the evidence mounts for the devastating effects on both brain and immunological development. This is one of the reasons I am so interested in research on other means of controlling bacterial infections (for example, bacteriophages (look here for example)).


[i] Loughman A., Ponsonby A.L., O’Hely A. et al. Gut microbiota composition during infancy and subsequent behavioural outcomes. EBioMedecine. 2020; 52: 102640. https://doi.org/10.1016/j.ebiom.2020.102640

2 Comments on “Microbiome Alterations by 12 Months and the Development of Behavioral Issues

  1. I think the same thoughts with regards to Matteo experience at birth .How can we ever forget that had our children not have had to have such strong antibiotics at birth that perhaps life would have been much better for them. I think this is also the reason vaccinations may have been more damaging then good. His 18 month shots he had an upset stomach and a fever like no other time. Relive those moments forever !

    • It’s impossible to not think that way, Toni, but I try my best to not. I try every day to look forward to the future, which I have some control over…rather than the past, which is already set. So hard sometimes though!

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