What causes autism? What we know, don’t know and suspect

It has long been a mystery why, but there is now extremely good evidence that the complex community of microbes in the gut plays an important role in human development and is essential for healthy immune and endocrine systems, as well as the brain.

Some scientists believe a disruption in the natural balance of these “good” bacteria may be a potential cause of autism. Antibiotics, for example, are commonly used with infants in Western societies and are known to kill “good bacteria” along with the “bad” bacteria for which they were prescribed.

A difference in the community of microbes, which humans have evolved to rely upon, may disrupt brain development and lead to autism. At the present time, the evidence for this potential cause of autism is not strong, but there will be substantial research in this area in coming years.


Autism has no one single cause, both in terms of genes and the brain. In a minority of cases, there are very clear genetic abnormalities that cause autism. In other cases, the genetic differences are more complex and yet to be discovered.

While there is currently no evidence for any environmental causes, it is possible subtle influences of the environment may affect individuals differently depending on their genetic make-up, leading to autism in some children. These relationships are also yet to be discovered.

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