Autism is not caused by a single factor but results from a complex interplay of genetic and environmental influences that affect brain development before and shortly after birth.

Genetic Factors

Genetics are the primary driver of autism, accounting for an estimated 60-90% of risk. Studies of identical twins show that if one twin has autism, the other has a 60-90% chance of also having it. Hundreds of genes have been implicated, each contributing a small amount of risk. In some cases, rare genetic mutations or chromosomal differences play a larger role.

Brain Development

Autism involves differences in how the brain forms connections during prenatal development. These differences affect how the brain processes social information, sensory input, and patterns. Research using brain imaging has identified structural and functional differences in multiple brain regions, but no single brain difference defines autism.

Environmental Influences

Environmental factors that may modestly increase risk include advanced parental age, certain prenatal complications, and specific medication exposures during pregnancy. These factors likely interact with genetic predisposition rather than independently causing autism. No environmental factor, including vaccines, diet, or technology, has been shown to cause autism on its own.

What Parents Should Know

Autism is nobody’s fault. It is not caused by parenting choices, lifestyle decisions, or anything parents did or failed to do. The most productive response to a diagnosis is pursuing early, evidence-based intervention. ABA therapy during early childhood can make a meaningful difference in your child’s development and long-term outcomes.