New Study on Gut Bacteria in Autism Unrelated to Wakefield Study

Color-enhanced scanning electron micrograph showing Salmonella Typhimurium (red) invading cultured human cellsCredit: Rocky Mountain Laboratories, NIAID, NIH, Lic. Wikipedia Commons

Color-enhanced scanning electron micrograph showing Salmonella Typhimurium (red) invading cultured human cells
Credit: Rocky Mountain Laboratories, NIAID, NIH, Lic. Wikipedia Commons

This article originally appeared in the Huffington Post on July 10 2013

A study published in the open access science journal PLoS ONE on July 3rd 2013 is starting to make the rounds in the alternative medicine community.  One site has already claimed that the new study serves to partially exonerate anti-vaccine dream-date Andrew Wakefield’s study on the role of gastro-intestinal (GI) symptoms in autistic children and his now falsified claim that the measles, mumps, and rubella (MMR) vaccine was the cause of not only the GI symptoms but of autism itself.  Reading these claims, it makes me wonder if any of the Wakefield supporters even read either of the studies, or even the abstracts, because a closer look reveals only the most tenuous of associations, and the retraction by the Lancet of Wakefield’s paper is not  in any way in jeopardy.

The new study out of Arizona State University by Kang et al compared the collection of normal bacteria found in the gut of autistic children with the collection, called the intestinal microbiome, in neuro-typical children.  The study of the microbiome and its effect on health has been an exciting area of research over the past several years, with connections between gut bacteria and mental health, heart and stroke, diabetes, and inflammatory bowel disease making their way into the news.  It is certainly known that uncomfortable and distressing GI symptoms have been associated with children diagnosed with Autism Spectrum Disorder (ASD) but the exact mechanism or even a vague notion of how to characterize the symptoms has been elusive.

The team at Arizona State analysed the stool samples of 20 children with ASD and 20 neuro-typical children. The analysis revealed difference in the diversity of specific types of bacteria, with statistically significant fewer bacteria from the genus Prevotella, and to a lesser extent Coprococcus and Veillonellaceae, in autistic children.  That is where most of the reporting ends in the mainstream press, but it is important to insert some caveats before conclusions can be drawn about the significance of the study.  First, the study failed to find any correlation between the severity of the GI symptoms and the severity of ASD, something that was not expected by the researchers.  Even more telling is there was no relationship found between the severity of the GI symptoms and the levels of difference in the microbiome: fewer Prevetolla species did not result in more GI symptoms.   The only correlation that this study found was between the overall decreased Prevotella and the diagnosis of ASD.

When we look at similar studies on the microbiome and ASD, different results have been found as well.  In 2010, a similar analysis did not find the same disparities as the Kang paper.  They found instead an increase in another bacteria species instead.  In a previous paper by one of Kang’s co-authors, Adams, they did find a correlation between GI symptoms and severity of ASD.  Because of this heterogeneity in the previous findings, all admitted by Kang et al in the paper, we cannot draw conclusions about what has caused these disparities in bacteria, only that they have occurred in this sample of these particular children.

Though it is technically complex, this study does seem thorough, it does not over reach in its conclusions, and is another step toward understanding the role of the gut in ASD.  What this paper does not have, however, is any relation to the discredited Wakefield study.  Wakefeild did not study the microbiome in any detail.  He did look for the evidence of parasites like Shigella, Salmonella and Campylobacter, but he did not assay the biome or look for any abnormalities in it.  There is just no relation to these two studies at all, other than a general interest in the connection between GI symptoms and autism.  Most definitely there is nothing we can conclude about the effects of the MMR vaccine on the microbiome, and anybody who is making these claims is making dangerous speculations

While it is understandable that the public is interested in the ongoing story of why ASD patients have so many problems with their gut and diet, we cannot leap beyond the conclusions from one study and overgeneralise.  This study, like any good science, leaves us with more questions than answers. Is there a connection between neurological symptoms and Prevotella?  Is the decreased incidence of Prevotella predictive of ASD? Is the severity of GI symptoms really connected to the severity of ASD?  Does the ASD cause the change in the microbiome, or does the microbiome cause ASD, or are both conditions interconnected in multiple ways?  Is there a genetic link between the ASD child and the microbiome and how is the microbiome of the child related to his or her immediate family?

What we do know is this will continue to be an active area of study for a long time to come, and Wakefield will still be left out in the cold.

6 Responses to “New Study on Gut Bacteria in Autism Unrelated to Wakefield Study”

  1. Bryan says:

    Of far more interest (and far more likely to indicate a causative mechanism) is the recent paper by Baumann et al, this week in translational psychiatry, showing that the mothers of many autistics have antibodies which recognize brain proteins.

    But the anti-vax types won’t like that one.

  2. Travis says:

    “it makes me wonder if any of the Wakefield supporters even read either of the studies, or even the abstracts, because a closer look reveals only the most tenuous of associations”

    Indeed, a very astute observation, Michael. It’s a not-so-subtle detail that the medical community fails to acknowledge. The paper is 15 years old, but it’s never too late to read it see what it actually says. It looked at only 12 children and it did not make a claim of causality between MMR and Autism. Yes, Andrew Wakefield does believe there is causality, but what the lancet published in 1998 did not make that claim.

    If you were to talk to a parent who, for example, has decided against giving their newborn a HebB shot, you’d likely find out that Andrew Wakefield has absolutely nothing to do with their decision. If one were to believe that Andrew Wakefield is solely responsible for the “anti-vaccine” movement, then I can understand the desire to constantly bring him up in discussion. But in my opinion, it’s the mainstream medical community that mentions his name far more often than the alternative medicine community.

    It is however, nice to see more and more research being done on the physical differences between children affected by ASD and neurotypical children. “Scientific Consensus” has evolved beyond the previous notion that ASD was the result of bad parenting. They’re now starting to come around to the notion that the gut is heavily involved. Next, they’ll get around to acknowledging that diet can play a role in managing the symptoms of affected children. Eventually, they’ll get around to acknowledging that incidence of ASD is in fact rising significantly.

  3. Lisa R. says:

    I can’t helpbeing skeptical of this study, noting that one of the authors is James B. Adams, a materials scientist and autism dad who’s been involved with a few studies of the kind where the method is just a means to a strongly desired finding.

  4. @Lisa

    Healthy skepticism is good – and given the conflicting evidence on the same topic, so I agree with you: conclusions really cannot be drawn from this study. The method had a lot of steps and some pretty complex tests so there was a lot of opportunity to introduce bias. That being said, the conclusion was very conservative and the authors did not overreach. Just because one of the authors has an autistic child, we cannot disregard the findings per se.

    I would like to see a larger study that focuses just on the predictive nature of the microbiome and autism diagnosis, given the findings of this study and with a much larger n.

  5. Lior says:

    Dear Mr. Kruse,

    The quacks are now using this one (also from PLos):

    For example, here:

    Any insights here?

    Thanks in advance and looking forward.
    Best regards,

  6. Thanks for the headsup Lior, this is not surprising.

    The PLoS ONE article of course does noting to mention any link between MMR and autism, but that does not stop the authors from The Liberty Beacon drawing their foregone conclusion of this link. The symptoms similar to IBS or Crohns are well established in autism and there may certainly be a ASD specific bowel dysfunction, as suggested by the paper, but a connection between MMR and ASD has not been established as of yet.

    It is also telling that the links to the papers supporting their ideas all come from the Mercola pubmed replacement.


  • Michael Kruse

    Michael is an advanced-care paramedic in York Region, just north of Toronto, Ontario. A semi-retired theatrical lighting designer as well, he re-trained in 2005 as an EMT-PS at the University of Iowa and as an ACP at Durham College, and is currently working towards a B.Sc at the University of Toronto. Michael is a founder and the chair of the board of directors of Bad Science Watch. He is also the recipient of the first annual Barry Beyerstein Award for Skepticism. Follow Michael on twitter @anxiousmedic. Michael's musings are his own and do not necessarily represent those of his employer or Bad Science Watch.