An estimated 1 in 36 children have autism in the United States according to a recent National Health Interview Survey.[1] Meanwhile, the Centers for Disease Control and Prevention (CDC) estimate that autism affects 1 in 54 children.[2] In either case, it’s clear that autism rates have been on the rise, as can be seen in the above graphic. 

The autism epidemic

Autism Spectrum Disorder (ASD) affects some 1.5 million children in the United States alone.[3] The lifetime cost of supporting an individual with ASD is estimated to be $1.4 million without intellectual disability, and $2.4 million with intellectual disability (about half of individuals with ASD have intellectual disability).[4] It is estimated that autism’s cost in the U.S. was $268 billion in 2015, projected to increase to $461 billion by 2025.[5] Incredibly, the CDC has recently estimated that 5.4 million U.S. adults also have autism spectrum disorder.[6]

What is the microbiome?

The microbiome refers to the community of microorganisms that share our body space.[7] The bulk of these microbes consist of bacteria with the largest concentration of bacteria found in the large intestine. There are actually more bacteria that live in and on us, than there are human cells in our body.[8] The gut microbiome alone has 150 times the number of genes that we have as humans.[9] This is all to say that the gut microbiome plays a significant role in determining our well-being affecting digestion, nutrition, immune function, and mental health.

What does the microbiome have to do with autism?

It’s recognized that genetics and environmental factors have a role in the etiology of autism.[10] Less often discussed, is the role of the microbiome in affecting autism spectrum disorders. A recent study found that children with autism tend to have an altered gut microbiota composition, suggesting an association between autism and the microbiome.[11] Furthermore, pre- and postnatal antibiotic exposure is associated with an increased ASD risk in children.[12]

Where does our microbiome come from?

The way in which we are born shapes our microbiome in a profound way. Newborn babies get their first major inoculation of microbes at the time of their birth. And this initial “seeding” of microorganisms lays the foundation for the development of the microbiome in the infant.

During pregnancy, the vaginal microbiome of the mother will typically shift to being predominated by probiotic Lactobacillus species of bacteria.[13] Babies that are born vaginally are then inoculated with these bacteria as they pass through the birth canal. But babies born via C-section bypass this microbial transfer (from mother to infant) and are instead colonized by a different set of microbes predominantly associated with skin bacteria.

C-sections and autism

A systematic review and meta-analysis found a 23% increased likelihood of autism spectrum disorder in offspring born via C-section delivery.[14] This doesn’t mean that C-sections cause autism, but rather that C-section delivery may predispose infants to be at greater risk of developing autism spectrum disorder due to differences in microbial inoculation at the time of birth (and subsequent early microbiome development in the infant). C-section delivery has also been linked to an increased incidence of asthma, obesity, and type 1 diabetes in offspring.[15]

The importance of the early microbiome

Researchers conducted an experiment where they randomly assigned 75 infants to receive either a probiotic (Lactobacillus rhamnosus) or a placebo during the first six months of life. 17% of the children in the placebo group went on to develop Attention Deficit Hyperactivity Disorder (ADHD) or Asperger syndrome – a mild form of autism spectrum disorder. Remarkably, the children who received the probiotic as infants had zero cases of ADHD or Asperger’s.[16] This study is described in more detail in the following video.

Breastfeeding reduces autism risk

Breastfeeding is estimated to contribute to 38% of the bacteria found in the infant gut during the first 30 days of life.[17] Breastmilk contains something called oligosaccharides – complex sugars that are indigestible by the infant, but act as a prebiotic selectively feeding the growth of beneficial Bifidobacterium strains.[18] These protective gut bacteria help to promote an anti-inflammatory state in the infant. Perhaps not surprisingly, a systematic review and meta-analysis found that exclusive breastfeeding was associated with a 76% decreased risk of autism spectrum disorder in offspring.[19] Breastfeeding for 12-24 months was associated with the most significant reduction in ASD risk.

Manipulating the microbiome to treat autism

Emerging evidence suggests that the microbiome can be manipulated to treat autism spectrum disorders as well. In one study, researchers gave 11 children with regressive-onset ASD a minimally-absorbed antibiotic called Vancomycin for 8 weeks. Autistic behaviors improved in the majority of the children during treatment, but these gains were lost after stopping the antibiotic, as can be seen below.[20] 

Treating autism with fecal transplants

Better and longer-lasting results were obtained in a more recent study, utilizing a two-week Vancomycin antibiotic treatment, followed by an 8-week modified fecal transplant therapy. On two-year follow-up, gastrointestinal symptoms in the children with autism saw an average improvement of 58%, and the severity of autism in these children saw an average reduction of 47% compared to baseline. At the beginning of the trial, 83% of the children were rated as having severe autism. Two years after the modified fecal transplant therapy, only 17% of the children were rated as severe, 39% were in the mild to moderate range, and 44% were below the autism spectrum disorder diagnostic cut-off scores.[21] These results are illustrated below.

Glyphosate and autism

Glyphosate (the active ingredient in the weed killer Roundup) is a patented antimicrobial agent[22] and the most widely used herbicide in the world. There is evidence in animals that glyphosate disrupts gut bacteria leading to an imbalance favoring overgrowth of toxic Clostridium species.[23] A recent systematic review showed an association between colonization of Clostridium bacteria in the intestinal tract and autism spectrum disorder.[24] Glyphosate has been found to contaminate popular children’s breakfast cereals.[25] Independent lab tests have even found glyphosate contamination in childhood vaccines.[26]

Other autism risk factors

Genetic syndromes, maternal diseases, environmental toxins, and certain pharmaceutical products have been implicated in the autism epidemic.[27] Their discussion, however, is beyond the scope of this article which focuses on the link between autism and the microbiome.

Unlocking the key to health

To learn more about leveraging the microbiome for better gut health, take my online course The Gut Microbiome: Unlocking the Key to Health

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