Calliope Holling, a psychiatric epidemiologist at the Center for Autism and Related Disorders at the Kennedy Krieger Institute in Maryland, says the study “validates a lot of what people have been thinking,” about whether the link between autism and the microbiome may be due in part to diet. “However, I think it does not completely erase the possibility that the microbiome plays a role in autism itself.”
One criticism, she says, is that the study looked at a snapshot in time, rather than over a long period. “Although the authors did not find that autism itself is related to the composition or diversity of the gut microbiome, this does not mean that the microbiome was not involved at some point, prior to the study, for example,” Holingue says. Yap acknowledges that in order to assess causation, longitudinal studies will be important.
While no study has yet shown this conclusively, early hints of a link between the gut and autism raised hopes for a treatment. For example, a research group at Arizona State University published a study in 2017 that included 18 children on the autism spectrum who also had digestive issues, and had their own feces cultured. In 2019, the team published a two-year follow-up, reporting a nearly 50% improvement in autism-related symptoms. But the study was not randomized, did not have a control group, was not compared to a placebo, and the sample size was small.
Arizona State University studies have been a source of controversy in the field, Holling says. “Some people like them a lot. And I think some other people are very concerned that they are doing more harm than good, and maybe the goal is not clear,” she says. One real source of disagreement between people with autism and their families has been whether the ultimate goal of the research is to find treatments. “A lot of the autism community has been very vocal in saying that they don’t want to focus research on autism therapies or autism treatments, but rather they want the comorbidities and things that support them,” Holingue says.
Although there is no concrete evidence to support efficacy, early research has encouraged clinics to offer treatments to people with autism, including interventions such as probiotics, prebiotics, fecal cultures, or FMTs (or often “transfusions”). Fecal transplants – in which microbes from a healthy person’s poop are administered to a patient either orally or orally – have been shown to be beneficial in some cases: specifically, in the treatment of Clostridium difficile colitis, a condition often debilitating, in some cases fatal times. From the overuse of antibiotics, the bacterial balance in the gut is obliterated. That success has turned into hype about trying the treatment on more and more conditions – including autism.
In people with autism or [their] James Cusack, chief executive of Autistica, a UK autism research charity, says families are receiving news that someone has autism, and they are left with only active support. “And this can be a very traumatic experience for families and for people with autism.” It also means that a parent may feel compelled to find alternative ways to ensure their child thrives in the same way as their peers. (One 2015 study surveyed parents and found that nearly nine out of 10 have sought complementary and alternative medicine for autism in their children.) These parents may be more likely to experience things that are not based on evidence at all, Cusack says. “And it’s really sad for people to be in this situation. What we should try to do is try to understand the reasons why people make these decisions and try to support them to take a different approach.”