It is well-known that gastrointestinal issues are pervasive among children with autism. While around one quarter of non-spectrum children experience regular gastrointestinal distress, around eighty five percent autistic children experience these problems (some reports claim it’s just over ninety percent). This has led to speculation that the microorganisms living in the gut (often called gut flora or gut bacteria) may be different in children with autism. Some have gone as far as to say that these gut issues are the cause of the autism, and believe that treating children on the spectrum with gluten-free/casein-free diets can reduce the symptoms of autism.
Several studies have been done to study the differences between gut flora of children with autism and healthy children and differences have been found. Children with autism are more likely to have larger amounts of Clostridia (a bacteria) living in their gut than healthy children. This bacteria is known to manufacture small amounts of neurotoxins that can get into the bloodstream and potentially affect the child. There are some instances of children with autism being administered an antibiotic and having some recovery and progress while they are taking the medicine, only to regress again after finishing the treatment. This suggests that some connection between gut bacteria and the expression of autism may exist.
It’s thought that these colonies of harmful bacteria can grow when very young children are given antibiotics for a common infection. The antibiotic kills off much of the gut flora, wiping out competition for the Clostridia or other harmful bacteria, which can then grow and send its toxins into the body. It is also possible that much of the harmful bacteria can make it into a young child’s body through contaminants in the environment.
In a study done recently, rats injected with propionic acid, a byproduct created by these bad bacteria showed developmental delays and disabilities similar to those expressed by humans with autism. While it used to seem ludicrous to suggest that serious diseases like autism could be caused by an imbalanced environment of gut flora, there is growing evidence that the important ecological balance in a human gut’s microbiome can be the key to good, or poor health.
Autism caused by bacterial overgrowth could explain the cases of autism that happens with “regression” when a child who is developing normally suddenly loses communication and social skills and can seem to become cold and withdrawn. The regression usually occurs between birth and 24 months. Often times the initial onset of autism is accompanied by a similarly sudden onset of gastrointestinal troubles such as diarrhea, constipation, and the like.
The theory that the micribiome of the gut could be affecting the brains of children with autism could also help explain how some parents see behavioral improvements with specific diets. Diets like a gluten/casein free diet or the specific carbohydrate diet are often recommended for children living with autism though there is little scientific proof they work. However, the idea that autism starts in the gut, rather than in a child’s DNA could explain why food choices may make a difference.
The idea that a bacterial infection could cause a life-long struggle with autism is a frightening one. But the gut flora theory of autism does have an upside; the disease could potentially be reversible if caught early enough. If it does turn out that autism is caused by bacterial overgrowth, it’s possible scientists will develop a way to diagnose and treat infants before they show overt symptoms, thus preventing them and their families from a life of living with autism.