by Dr Giacomo Vivanti
Many individuals with Autism have Intellectual Disability (that is, below average I.Q. and poor adaptive functioning). What is the nature of this association? Data published from a recent study at the Olga Tennison Autism Research Centre (OTARC), Intellectual development in autism spectrum disorders, provide new insight into this complex issue.
The scientific community has given little attention to this question for decades. Indeed, the prevalent view in the field is that Intellectual Disability in autism is an additional, unrelated condition that ‘happens’ to be present in some individuals with autism , and is not seen as providing valuable information on the nature of autism.
Following this line of thought, most research in autism conducted over the past decades, including research on treatment, has excluded individuals with autism who have an Intellectual Disability, on the ground that their Intellectual Disability would confound the interpretation of results. As a consequence, we don’t have much knowledge on effective treatments for children with lower IQ (arguably the ones that are more in need of help) and we don’t know much about why Intellectual Disability occurs so often in autism.
However, the data published in our study provide some new insight into this complex issue. Results from a longitudinal analysis of the intellectual development of 80 children with autism indicate that the risk of developing an Intellectual Disability increases with the severity of autism symptoms. In other words, those children who are more severely affected by autism in early development are more likely to have a lower I.Q. later in life.
Why is this the case?
Recent research on brain plasticity indicates that brain organization in typical development is critically shaped by the child’s social learning experiences during early development. We propose that the presence of severe symptoms of autism impedes this process, so that children who are more severely affected are those who are least able to appropriately engage in the social learning experiences that are crucial for normal intellectual development. Therefore, autism and Intellectual Disability do not appear to be unrelated conditions. Rather, the presence of severe autism symptoms might be a risk factor for developing Intellectual Disability. That is, the children with “autism associated with Intellectual Disability” are in fact children whose autism symptoms are so severe that these preclude them from processing the environmental inputs that ‘sculpt’ brain organization during early critical periods.
From this perspective, we argue that the practice of excluding children with Intellectual Disability in autism research to study “pure autism unconfounded by Intellectual Disability” is ill considered. Rather, research should target those factors that place affected individuals at an increased risk of negative outcomes, such as the presence of an Intellectual Disability, and understanding the underlying causal mechanisms, to inform clinical practice, with the ultimate goal of fostering positive outcomes for all individuals with autism .
How to read and download the article
The article Intellectual development in autism spectrum disorders has been made available without cost to you. When you click through to the extract, the top right hand side column provides numerous formats including PDF and full text.