Parents' first concerns about toddlers with autism spectrum disorder: effect of sibling status.

Herlihy et al. (2015) asked parents when they first worried about their toddler who was later diagnosed with autism. They grouped the toddlers by sibling status: those with an older autistic sibling, those with only typical siblings, and only or oldest children.

The team compared the age parents first raised concerns across the three groups. No tests or treatments were given; the study was a survey of parent memories.

Parents who already had an autistic older child sounded the alarm earliest, around 10 months. Parents with only typical siblings spoke up later, around 14 months. Only or oldest toddlers were flagged latest, around 16 months.

The gap between first and last group was half a year. That delay can push back screening and early intervention.

Ederer et al. (2026) extends the story: caregivers of infant siblings already feel higher stress by 12–18 months. The earlier concern timing in Lauren et al. may be driven by these stressed, watchful parents.

Cohen et al. (2018) and Hampton et al. (2015) show parent checklists can spot ASD risk in high-risk siblings as early as 6–12 months. Lauren et al. adds the real-world timing: parents in these same high-risk families naturally voice worries months before other families.

Toth et al. (2007) foreshadowed the finding by showing that non-autistic toddler siblings already had language and social lags. Lauren et al. now shows parents notice such lags sooner when they have an older autistic child to compare against.

If you screen an only or oldest toddler, dig deeper and ask about early signs parents may have dismissed. Offer extra education on red flags at 12-month visits. For families with an autistic older sibling, harness their early awareness—provide screening tools at 6–9 months so their heightened watchfulness leads to action, not just worry.