Neuropsychological functioning of siblings of children with autism, siblings of children with developmental language delay, and siblings of children with mental retardation of unknown genetic etiology.

Pilowsky et al. (2007) compared brothers and sisters of three groups: kids with autism, kids with language delay, and kids with unknown-cause intellectual disability.

They gave each sibling a full neuropsych battery. Then they removed any sibling who already had a developmental diagnosis.

The goal was to see if autism carried a unique cognitive fingerprint in unaffected brothers or sisters.

After the team pulled out diagnosed siblings, the remaining autism-group brothers and sisters scored the same as the other two groups on every test.

No special memory gap, no extra attention problem, no single marker said 'this family carries autism risk.'

Yaldız et al. (2021) later asked teenagers how often they felt anger or sadness. They also found no difference between siblings of kids with developmental delay and control siblings. Two different labs, two different measures, same null result.

Laposa et al. (2017) looked deeper into feelings and saw a twist: adolescent siblings of kids with IDD did report more anxiety toward their brother or sister. Tammy’s study did not ask about emotions, so the papers do not clash—they simply map different terrain.

Lee et al. (2021) scoping review pulls all these sibling studies together and adds one big warning: culture changes everything. A calm cognitive profile in one country may hide heavy caregiving stress in another. So read Tammy’s ‘no difference’ finding alongside culture-first papers before you plan services.

If you screen siblings hoping for an autism-specific cognitive red flag, you will not find it. Instead, watch for general learning or language delays no matter the brother’s or sister’s diagnosis. When worry shows up, ask about family stress and cultural roles—those factors predict need better than any single test score.