Genetics have been shown to have a prominent role in the development of ASD. Numerous studies have shown that ASDs have a strong genetic component with most estimating heritability from 70 to 90%.
In the vast majority of cases, autism seems to be a multi-gene disease, involving variations of several genes in variable proportions and locations.
A recent study reported that recurrence risk for siblings of affected children is 18.7%, a 20-fold increase compared to the prevalence of autism in the general population. The authors also report differential recurrence risks based on gender (25.9% for males and 9.6% for females).
While many studies have demonstrated a strong genetic basis for autism spectrum disorders, the identification of numerous genetic markers shown to be associated with autism demonstrate a complex inheritance pattern. Additionally, genetic testing for autism is utilized to identify copy number variants (CNVs) having a strong association with autism. These CNVs are found in less than 10% of affected individuals. Adding de novo rare mutations to such CNVs or others chromosomal rearrangements only explain 10 to 20% of autism cases.
Recently, a number of common genetic variants or SNPs (single nucleotide polymorphisms) have been strongly linked to autism. While individual SNPs are not on their own sufficient to be causal, recent studies have shown that the combination of autism associated SNPs may markedly increase the risk of autism in siblings of affected children.
Click here to learn what a SNP is.