Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition characterized by challenges in social interaction, communication, and behavior. Much about ASD remains elusive and diagnosing it is notoriously difficult. However, a groundbreaking study published in Nature Microbiology explored the relationships between ASD and the gut microbiome, suggesting that a simple fecal test could help diagnose the condition.

Autism and gut flora

According to the Centers for Disease Control and Prevention (CDC), about 1% of the world’s population has autism spectrum disorder. Despite this relatively high incidence, it is notoriously difficult to understand and diagnose.

ASD is typically diagnosed through a combination of behavioral assessments and developmental evaluations. The diagnosis involves screenings and check-ups, followed by comprehensive evaluations by psychologists and developmental pediatricians. Early and accurate diagnosis is crucial for accessing appropriate interventions and support and yet, it’s so hard to diagnose.

This is where the gut bacteria comes in.

Several studies over the past few years have highlighted a potential link between our gut microbiome (not just bacteria, but also viruses, fungi, and archaea) and ASD. This connection isn’t perfectly understood, but a link between ASD and gut flora seems very likely.

Researchers led by Prof. Qi Su at the Chinese University of Hong Kong wanted to see whether this connection could also be used for a diagnosis.

A new diagnosis of autism

The researchers performed metagenomic sequencing on fecal samples from 1,627 children aged 1 to 13 years, with and without ASD. Metagenomic sequencing is a method that scientists use to study all the genetic material from a group of microorganisms in a sample, like soil or feces, to understand which microbes are there and what they might be doing.

This extensive analysis revealed significant differences in the gut microbiota composition between children with ASD and neurotypical children. They found dozens of bacteria, archaea, viruses, and fungi that were significantly altered. Then, using advanced machine learning techniques, they created diagnostic models. Ultimately, they developed a microorganism panel of 31 markers that incorporated different types of organisms, not just bacteria. With this approach, they were able to identify ASD with up to 82% accuracy.

“This study applied high-quality statistical and machine learning analyses and have identified both members of the gut microbiome and biological pathways that can discriminate ASD which also carry biological plausibility,” says Dominic Farsi, Associate in Nutritional Sciences, King’s College London, in a reaction for the Science Media Centre.

“These results are novel and could have great potential in diagnostic practice, however, it is important to highlight they are novel, and further research is required to further validate these findings. Notwithstanding, these results could represent a big step towards enhancing diagnostic methods for ASD and developing the mechanistic evidence base.”

Bhismadev Chakrabarti, Research Director of the Centre for Autism at the University of Reading, who was not involved in the study, echoed the idea. He remarked that this reveals a new way to look at autism.

“This study broadens our understanding by including fungi, archaea, and viruses, where previous studies have largely focused on the role of gut bacteria in autism. The results are broadly in line with previous studies that show reduced microbial diversity in autistic individuals.”

“What is exciting about this study is that it opens up the possibility of investigating specific biochemical pathways and their impact on different autistic features. It could also provide new ways of detecting autism, if microbial markers turn out to strengthen the ability of genetic and behavioural tests to detect autism. A future platform that can combine genetic, microbial, and simple behavioural assessments could help address the detection gap.

Plenty of work still left

Although genetic factors play an important role in autism, the microbiome has increasingly been shown to also play a role. Su suspects it could perhaps modulate immune responses and neurotransmitter production.

However, this does not necessarily imply causation, the researcher notes. In other words, we don’t know what’s causing what. But if the researcher is right and gut flora is at least linked to the severity of autism, it also raises the potential for autism treatments.

Targeted therapies, such as personalized probiotics, dietary interventions, and microbial transplants, could be developed to modify the gut microbiota composition and improve gut health, potentially alleviating some ASD symptoms. Fecal transplants are already showing promise in reducing the severity of ASD.

Although there’s still plenty of work left to confirm the findings, the new study marks an important advancement in our understanding of the microbiome’s role in ASD. It’s becoming abundantly clear that a number of different organisms play a role in this. This knowledge can, at the very least, be used to diagnose ASD faster. It could also result in developing customized treatments or interventions, offering better outcomes and improving the quality of life for individuals with ASD.

The study was published in Nature Microbiology.