Autism spectrum disorder results from a complex combination of genetic factors, brain development differences, and, to a lesser extent, environmental influences. No single cause has been identified, and for most individuals, autism likely results from the interaction of multiple factors.

Genetic Factors

Genetics account for an estimated 60-90% of autism risk. Twin studies show high concordance rates, and sibling recurrence risk is about 20%. Over 100 genes have been implicated, each contributing a small amount of risk. In about 10-20% of cases, a specific genetic cause can be identified, such as Fragile X syndrome or Rett syndrome.

Brain Development

Autism involves differences in how the brain forms and organizes during prenatal and early postnatal development. These include altered patterns of neural connectivity, differences in brain structure and volume, and variations in neurotransmitter systems. The brain of an autistic individual is not damaged; it is organized differently from the earliest stages of development.

Environmental Contributions

Environmental factors that may modestly influence risk include advanced parental age, certain prenatal infections, some pregnancy complications, and specific medication exposures during pregnancy. These factors appear to interact with genetic susceptibility rather than causing autism independently.

What Does Not Cause Autism

Vaccines do not cause autism. Parenting style does not cause autism. Diet, screen time, and wireless technology do not cause autism. These myths have been thoroughly investigated and debunked by rigorous research.

Focus on Action

Understanding causes is less important for families than accessing effective treatment. Early intervention with ABA therapy produces meaningful improvements regardless of the specific factors that contributed to a child’s autism.