By Jeffery L. Hayden, PhD, BCBA-D and Jane McCready
“The objective difference between people with autism and the general population will disappear in less than 10 years. The definition of autism may get too vague to be meaningful.”
—Dr Laurent Mottron, Université de Montréal
“We found a marked decline in the inclusion of people severely affected by autism in clinical research, even using a very liberal definition of severity.”
—Matthew Siegel, Tufts University School
Three recent studies have demonstrated that research has been increasingly marginalizing individuals with severe forms of autism spectrum disorder (ASD).
In an article published last month in JAMA Psychiatry, Rodgaard and colleagues examined the scientific literature from 53 years, 1966 through 2019, to determine if and how the differences between ASD subjects and control (normal) subjects changed over time. The authors also examined how these changes correspond to changing definitions of ASD and the associated increases of those diagnosed with ASD.
They found that the differences between those with and without ASD has decreased over time, in other words from what was once a homogenous group to a heterogenous one. This is worrisome, they said, because the growing heterogeneity may create challenges for research. They said:
“[G]radual changes to a diagnostic category, such as autism, and blurring of the distinction between autistic traits and autism could potentially affect our ability to advance mechanistic models of the condition. The belief within autism research that large heterogeneous populations are preferable compared with small narrowly defined ones in the search for scientific truth may be open to question.”
In other words, by diluting what we mean by “autism” we are losing the ability to find meaningful commonalities in biology and treatment, to the detriment of those with ASDs. What may be true for severe autism may be very different for those with HFA, and lumping together drowns out distinctions.
Research on severe forms of autism is also increasingly marginalized from a raw numbers perspective. Stedman and colleagues earlier this year investigated how much those with severe forms of ASD are included in treatment studies. The study authors examined 367 treatment studies published in the scientific literature in the 22 year period between 1991 through 2013. The study analysis found that with each year, starting with 1990, there was a 16.5% decrease in representation of those with severe forms of ASD in published treatment studies. Starkly put for the chances of any research getting done with those at the severe end of the autism spectrum: “the proportion declined substantially from more than 90 percent in the early 1990s to just 30 percent in the 2010s.” The authors state that without full representation in research of the entire spectrum of ASD, we may “leave behind those with arguably the greatest need.”
Fading away: As research becomes increasingly saturated with cases of milder forms of autism, severe autism has become marginalized.
In March this year, a UK study pointed to an even worse situation. Researchers from the University of Exeter and University College, London examined all high quality autism studies worldwide in a particular year, 2016, and discovered that only 6% of participants were autistic people with a learning disability. The exclusion of half of the spectrum was near complete.
Together, these three studies should serve as a clarion call to those who work with, advocate for, and/or love individuals with severe forms of ASD. Representation and research are key to effective advocacy, and with the boundaries of what is and what is not ASD becoming less clear, those with severe forms of ASD are at risk of getting lost in the mix.
The alarms are ringing.
References:Rodgaard E, Jensen K, Vergnes J, Soulieres I, and Mottron L (2019). Temporal changes in effect sizes of studies comparing individuals with and without autism: A meta-analysis. JAMA Psychiatry. https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2747847.
Stedman A, Taylor, B, Erard, M, Peura, C, and Siegel, M. (2019). Are children severely affected by autism spectrum disorder underrepresented I treatment studies? An analysis of the literature. Journal of Autism and Developmental Disorders, 49, 1378-1390.https://doi.org/10.1007/s10803-018-3844-y
Russell G, Mandy W, Elliott D, White R, Pittwood T, Ford T. (2019). Selection bias on intellectual ability in autism research: a cross-sectional review and meta-analysis. Molecular Autism. https://molecularautism.biomedcentral.com/articles/10.1186/s13229-019-0260
https://www.disabilityscoop.com/2019/03/19/kids-severe-autism-overlooked/26209/