The Microbiota In Autism

Although it is a disease associated with neurological disorders, the microbiota in autism is altered. In fact, most autistic people suffer from gastrointestinal problems and immune system disorders. In this article you will discover how the intestinal flora is related to this disorder.

The gut microbiota

Children with autism have different microbial composition in the gut than other infants. The composition of the gut microbiota is different in the stomach, small intestine and in the colon. Thus, the thousands of microbial species -bacteria, viruses and some fungi- that inhabit it comprise the main protection system of the gastrointestinal tract.

The microbiota participates in the proper functioning of the body in different ways:

  • Establishing an intestinal barrier that selects the passage of different substances, preventing pathogenic species from crossing it.
  • Maturing the immune system, stimulating innate and acquired immunity.
  • Taking care of the synthesis and metabolism of nutrients, hormones and vitamins, in addition to the elimination of toxic substances.

The modifications of the bacterial composition of this microbiota are influenced by diet, the use of antibiotics, lifestyle and genetics. Recent studies suggest that there could be a relationship between flora alterations and some psychiatric disorders – autism, schizophrenia, Parkinson’s disease.

Brain-gut connection

Dysbiosis is the alteration in the intestinal bacterial composition that leads to the production and spread of lipopolysaccharide (LSP) to the blood, a pro-inflammatory endotoxin. This molecule influences the modulation of the central nervous system, controlling emotions.

There is a bidirectional connection between the central nervous system and the gut. Neurons can change the microbial composition of the intestinal flora and alter intestinal permeability. In this way, the brain directly influences the gut microbiota.

On the other hand, there are publications that show that this microbiota controls the activities of the central nervous system. A study in the journal Brain, Behavior and Immunity investigated how the bacterium Campylobacter jejun i raised the anxiety state of mice.

gut microbiota in autism

Autism spectrum disorder (ASD)

This disorder encompasses a set of neurological changes that are characterized by restricted and repetitive behavior, as well as a deficit in social interaction and communication.

People with autism are often treated with antibiotics to medicate other underlying conditions, such as chronic otitis media. This affects the protective gut microbiota and facilitates the colonization of bacteria that produce neurotoxins.

In addition, many children with autism suffer from gastrointestinal problems, such as inflammatory bowel disease (IBD), which manifest with:

  • Diarrhea
  • Constipation
  • Abdominal pain
  • Vomiting
  • Sleep disorders
  • Irritability

Microorganisms of the microbiota in autism


Clostridia are found in higher concentration in patients with ASD. Many of these bacteria are beneficial and are part of a healthy gut microbiota. However, there are pathogenic species, such as C. tetani and C. perfrigens, that produce toxins and cause serious diseases in humans.

In a study published in the Journal of Child Neurology, children with regressive autism were treated with vancomycin and an improvement in gastrointestinal symptoms and neurological behavior was observed in most of them. This points to the influence of the microbiota in autism and its possible modification.


This bacterium has been found in biopsies taken from the lining of the gastrointestinal tract and from feces of children with ASD. Sutterella is considered the main component of the microbiota in children with autism, as it is hardly found in other people.

Desulfovibrio, Lactobacillus and Bifidobacterium

Desulfovibrio species are related to the most serious symptoms of autism. They are producers of propionic acid, which seems to be associated with the pathogenesis of ASD.

Finally, lactobacilli are also found in higher concentrations in patients with ASD. And bifidobacteria are present in less abundance than normal.

child with autism in front of a shadow

Treatments for alterations of the microbiota in autism

As the microbiota appears to play an important role in the pathophysiology of ASD, treatments are based on modifications of the bacterial composition. It is intended to restore balance so as not to alter the nervous system. Some options tested are:

  • Probiotics: Probiotics have the ability to normalize the microbiota and intestinal problems. It is used as an alternative to treat gastrointestinal and autism symptoms.
  • Fecal microbiota transplantation: through this procedure, the fecal microbiota is transferred from a healthy person to a patient suffering from dysbiosis. It has been carried out to treat cases of inflammatory bowel disease, in addition to improving symptoms of constipation.
  • Diet: Children with autism have problems with eating. These children eat less fruits, vegetables, and protein. Therefore, an improvement in your diet could help the health of your gut microbiota.
  • Antibiotics: despite the fact that these compounds produce alterations in the microbiota, specific drugs have been tested, such as vancomycin or minocycline.

Microbiota in autism: a field of research

The influence of the gut microbiota in children with autism appears to be well founded. In any case, it becomes essential to continue with the investigations to have more certainties. For now, if you have a family child with autism, you should consult with specialists in the field to choose the best approach to their problem.

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