Measurement of nonverbal IQ in autism spectrum disorder: scores in young adulthood compared to early childhood.
Half of toddlers diagnosed with ASD can reach average IQ by age 9 if they get enough early-intervention hours.
01Research in Context
What this study did
Ohan et al. (2015) tracked the kids diagnosed with ASD at age 2. They gave each child the same IQ and language tests again at age 9.
The team wanted to know how many kids moved into the average cognitive range and what early factors predicted that jump.
What they found
By age 9, over half scored in the average IQ range. Almost 9 out of 10 used useful, everyday speech.
Children who got more early-intervention hours before age 3 had the best odds of catching up.
How this fits with other research
Reichow (2012) pooled five meta-analyses and also found medium IQ gains after early intensive ABA. The new numbers line up with those averages.
de Jonge et al. (2025) followed the same kids into adulthood. They show that early non-verbal mental age plus at least 20 parent-coaching hours forecast who keeps climbing on daily-living skills. Together the studies trace a long arc: early cognitive gains at 9 foreshadow adult independence.
Sievers et al. (2020) give us adult finish lines. They say "good outcome" looks different by ability level: less-able adults need daily skills above an 8-year level and regular activities; more-able adults need paid work, independent living, and at least one close friend. L et al.'s kids who reach average IQ by 9 are the group most likely to hit the higher bar.
Why it matters
Your intake assessment at age 2 is not a ceiling. Push for intensive, parent-involved intervention right away and keep measuring. Use the Mullen or similar tools yearly; celebrate when scores cross into the average band, but keep goals ability-specific as clients grow.
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02At a glance
03Original abstract
The purpose of the present study was to examine the developmental outcomes of children 7 years after their initial diagnosis. Children diagnosed with autism or PDD-NOS at age 2 received follow-up evaluations at age 9. Diagnostic stability was high, with 88 percent of the sample obtaining autism spectrum diagnoses at age 9. Cognitive scores improved considerably for a large segment of the sample, with over 50 percent obtaining scores in the average range at follow-up. Language outcomes were also positive at follow-up; 88 percent of the sample demonstrated at least some functional language, and 32 percent were able to engage in conversational exchanges. Early characteristics that predicted outcome status were: age of diagnosis, age 2 cognitive and language scores, and total hours of speech-language therapy between ages 2 and 3. These findings highlight the potential long-term benefits of both early identification and early intervention, and provide additional evidence for the importance of promoting public awareness of the early signs of autism.
Journal of autism and developmental disorders, 2015 · doi:10.1177/1362361306063296