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Understanding autism
Understanding autism

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5.1 Autism in families

As you learned in Week 1, twin studies provide evidence for a strong genetic factor in autism. When one twin of a pair is on the autism spectrum, the chance of the other twin also being on the spectrum (known as concordance) is much higher if these twins are identical than if they are fraternal. Identical twins have identical genes, whereas fraternal twins are no more alike genetically than, say, two brothers or two sisters. Identical twins and fraternal twins are likely to be very similar in their experiences of the environment. Therefore, the higher concordance for autism in identical twins suggests that the predisposition to develop autism is strongly genetic.

Even in non-identical twins or in siblings, concordance for autism is higher than in the neurotypical population. Twin and sibling concordance findings together suggest that autism can be passed down (inherited) from one generation to another, and affect multiple members of the same family. This was illustrated in video clips in Week 3: brothers Acis and Harry [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)]   and their grandfather John are all on the autism spectrum.