Autism spectrum disorder (ASD) is a developmental disability caused by differences in the brain. There is no single known cause of ASD, and given the complexity of the disorder, there are probably many causes. Both genetics and environment may play a role. Some of the known causes of ASD include:
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Genetics: Several different genes appear to be involved in ASD. Changes in certain genes increase the risk that a child will develop ASD. If a parent carries one or more of these gene changes, they may get passed to a child (even if the parent does not have ASD). Other times, these genetic changes arise spontaneously in an early embryo or the sperm and/or egg that combine to create the embryo.
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Environmental factors: There is a range of environmental influences that may contribute to ASD. For example, exposure to certain chemicals or toxins during pregnancy may increase the risk of ASD. Extremely preterm babies born before 26 weeks of gestation may also have a greater risk of ASD.
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Brain biology: Most of the genetic and environmental influences that give rise to ASD appear to affect crucial aspects of early brain development. Some appear to affect how brain nerve cells, or neurons, communicate with each other. Others appear to affect how entire regions of the brain communicate with each other.
It is important to note that vaccines do not cause autism. While neurological disorders like Alzheimer’s disease or Parkinson’s disease have well-defined pathologies, ASD and other psychiatric disorders have had a lack of defining pathology, challenging efforts to develop more effective treatments.
