Prevalence of autism in an urban population of adults with severe intellectual disabilities--a preliminary study.
Screen adults with severe ID for autism—prevalence is high (1 in 5) and often missed.
01Research in Context
What this study did
Doctors in Reykjavik checked the adults who already had severe intellectual disability (ID).
They gave each adult the ADOS and ADI-R to see if autism was also present.
What they found
One in five adults (21 %) met full criteria for autism spectrum disorder.
Only half of those cases had been flagged by service records before the study.
How this fits with other research
Hastings et al. (2001) counted autism in the whole Icelandic population and saw rates rise across decades. Smith et al. (2010) zoomed in on adults with severe ID and found an even higher share, showing the rise is not just a kids’ issue.
Meir et al. (2012) built a new pain scale for the same adult-ID group. Together the papers warn that if you miss autism, you may also miss pain signals that look like "behavior."
Mahdi et al. (2018) later showed autism functioning covers 110 life areas. E et al.’s high prevalence number gives BCBAs a reason to screen broadly, not just for core autism traits.
Why it matters
If you serve adults with severe ID, plan on every fifth client also having autism. Add ADOS items to your intake, write visual schedules, and train staff on sensory breaks. Early recognition turns vague "problem behavior" into treatable autism-related needs and opens doors to ABA funding.
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02At a glance
03Original abstract
BACKGROUND: Research on the prevalence of autism in Iceland has indicated that one possible explanation of fewer autism cases in older age groups was due to an underestimation of autism in individuals with intellectual disabilities (IDs). The present study systematically searched for autism cases in the adult population of individuals with severe ID living in the city of Reykjavik, Iceland. METHODS: Potential participants (n = 256) were recruited through the Regional Office for the Affairs of the Handicapped in Reykjavik. First, a screening tool for autism was applied, followed by the Childhood Autism Rating Scale and finally the Autism Diagnostic Interview-Revised (ADI-R). RESULTS: The point prevalence of severe ID was 3.7/1000 (95% CI 3.2-4.1) with a male-female ratio of 1.2:1. Participation rate in the study was 46.5%. Participants were younger than non-participants and more often residents of group homes. The prevalence of autism was 21% (25/119) (95% CI 14.7-29.2) with a male-female ratio of 1.8:1. Of the individuals with autism, 10/25 (40%) were verbal according to the ADI-R definition, and 18/25 (72%) had active epilepsy and/or other neurological conditions and handicaps. CONCLUSION: The study identified twice the number of autism cases than those previously recognised within the service system. Autism is a prevalent additional handicap in individuals with severe ID, which should always be considered in this population. There are indications that the estimated prevalence of autism found should be considered minimal.
Journal of intellectual disability research : JIDR, 2010 · doi:10.1111/j.1365-2788.2010.01300.x