Autism is caused by a combination of multiple genetic and environmental factors rather than a single known cause. Genetic influences play a significant role, with some cases linked to rare gene mutations and common genetic variations that together increase the likelihood of autism. Environmental factors that may interact with these genetic predispositions include advanced parental age, prenatal exposure to air pollution or certain pesticides, maternal obesity, diabetes or immune system disorders, extreme prematurity or very low birth weight, and birth complications involving oxygen deprivation to the baby's brain. Notably, vaccines have been extensively studied and found not to cause autism. The exact interplay between genes and environment is complex and still under investigation, with no single factor responsible for the condition.
Genetic Factors
- Autism has a strong genetic component, with heritability estimated between 60% and 90%.
- Some cases result from rare gene mutations, while others involve many common genetic variants with small individual effects combined.
- Spontaneous mutations in parental sperm or egg may also contribute.
- Certain genetic syndromes, like Fragile X, Down, and Rett syndromes, are associated with autism.
Environmental Influences
- Factors mostly relate to prenatal and perinatal periods, such as parental age, exposure to pollutants or pesticides during pregnancy, maternal health conditions, premature birth, and oxygen deprivation at birth.
- These environmental factors do not directly cause autism alone but may increase risk in genetically susceptible individuals.
Disproven Theories
- Earlier claims that vaccines caused autism have been thoroughly researched and disproven by numerous studies globally.
The current scientific consensus emphasizes autism as a neurodevelopmental condition arising from complex genetic and environmental interactions rather than a single cause.
