When your child receives an autism diagnosis, one of the first questions that surfaces — often with guilt attached — is: did this come from us?
The answer is yes, in significant part. Autism has a strong genetic component — one of the strongest of any neurodevelopmental condition. But it is far more complex, and less deterministic, than many assume.
What the Research Shows
Twin studies consistently show that if one identical twin is autistic, the other is autistic in 60–90% of cases. For fraternal twins it's around 30% — still significantly higher than the general population rate of 1–2%.
A major 2019 study in Nature Genetics estimated approximately 80% of the risk for autism is attributable to inherited genetic factors.
Source: Sandin et al., 2017, JAMA; Tick et al., 2016, JCPP
In Ireland prevalence is estimated at approximately 1 in 65 children per NCSE data — likely higher in reality due to underdiagnosis.
What Genes Are Involved?
There is no single "autism gene." Hundreds of genes are associated with increased risk, each contributing a small amount.
1. Common variants: small variations in hundreds of genes contributing cumulative risk. This is why autism tends to run in families.
2. Rare de novo mutations: new mutations not inherited from either parent. Conditions like Fragile X, Rett syndrome and Tuberous Sclerosis have high autism prevalence.
Does Autism Run in Families?
Yes — and many parents notice it only after their child's diagnosis. Family history viewed through a new lens. The broader autism phenotype (BAP) — traits that don't reach diagnostic threshold — is far more common in families of autistic individuals.
If any of this resonates — you don't have to figure it out alone. Amanda offers free initial consultations.
Book a Free CallWhat About Environmental Factors?
- ♥Advanced parental age at conception
- ♥Premature birth and low birth weight
- ♥Prenatal exposure to certain medications (notably valproate)
- ♥Complications during pregnancy or birth affecting brain development
What does not cause autism: vaccines, parenting style, diet, screens, or socioeconomic background. The MMR/autism link from Wakefield's 1998 fraudulent study has been conclusively disproven.
Should Other Family Members Be Assessed?
A personal decision. Siblings of autistic children are assessed at a higher rate for good reason. Speak to your GP.
Genetics does not mean predetermination. You didn't cause this. And you can absolutely help.