Cross-sectional evidence for a decrease in cognitive function with age in children with autism spectrum disorders?
IQ scores in autism don't follow a simple decline pattern - individual trajectories vary widely, so track each child separately.
01Research in Context
What this study did
Houwen et al. (2014) compared IQ scores across age groups in children with autism. They tested one group of 6-7 year-olds and another group of 8-18 year-olds. The study used standard IQ tests to look for age-related changes.
What they found
Older children with autism scored lower on overall IQ than younger children. The biggest drops were in attention and verbal comprehension skills. This suggests cognitive abilities may decline with age in autism.
How this fits with other research
Peristeri et al. (2024) directly contradicts these findings. Their 4-year study of preschoolers with autism found mixed IQ trajectories - some children improved while others declined. This challenges the idea of universal decline.
Huguenin et al. (1980) seems to contradict too, showing adaptive skill gains with age. But this apparent contradiction makes sense - their sample included children with intellectual disability, while Suzanne's sample had higher-functioning children. Different IQ ranges explain the different results.
Flapper et al. (2013) extends these findings by showing slower receptive vocabulary growth in boys with autism. This supports the verbal comprehension weakness Suzanne found in older children.
Why it matters
Don't assume an autistic child's IQ will naturally decline after age 8. The cross-sectional design may mask individual differences. Some children improve, others stay stable, some decline. Track each child's trajectory rather than expecting decline. When you see lower scores in older children, consider testing anxiety, motivation, or other factors before concluding cognitive deterioration.
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02At a glance
03Original abstract
Autism spectrum disorders (ASD) are associated with early disturbances in brain maturation processes and these interferences presumably have their consequences for the progressive emergence of cognitive deficits later in life, as expressed in intelligence profiles. In this study, we addressed the impact of age on cognitive functioning of 6- to 15-year-old children and adolescents with ASD. Intelligence profiles were measured by the Wechsler Intelligence Scale for Children and compared among four consecutive age cohorts (children aged 6.17-8.03 years, 8.04-9.61 years, and 9.68-11.50 years and adolescents aged 11.54-15.85 years) of 237 high-functioning boys with ASD. The results clearly demonstrated that the global intelligence level was lower in children aged 8 years and older, when compared with 6- and 7-year-old children with ASD. This is mostly due to the Freedom From Distractibility factor, suggesting that older children were less able to sustain their attention, they were more distractible, or had more graph motor difficulties. Moreover, an effect of age was also found with respect to the relatively poor performance on the subtest Comprehension when compared with other verbal comprehension subtests, indicating that specifically the impairments in verbal comprehension and social reasoning abilities were more profound in older children when compared with 6- and 7-year-old children with ASD. Findings of this cross-sectional study showed that it is relevant to take age into account when evaluating the impact of cognitive impairments on intelligence in children with ASD, because the impact of these developmental disorders might be different at different ages.
Autism research : official journal of the International Society for Autism Research, 2014 · doi:10.1002/aur.1380