Still a Grey Zone in Diagnostic Boundaries for Autism Spectrum Disorder

The Diagnostic and Statistical Manual of Mental Disorders (DSM-5), which was released in May 2013 by the American Psychiatric Association, has redefined the autism spectrum, and notable changes include dropping Asperger syndrome and pervasive development disorder not otherwise specified (PDD-NOS). How the changes in classification will affect diagnosis are still not clear but the commentary highlights that although there are some improvements there is still a lack of clarity with the new system, and researchers say diagnostic consistency remains hard to achieve.
The overview, which was conducted by Murdoch Childrens Research Institute and the University of Melbourne, looked at international prevalence rates, possible causes of autism and the evidence and lack of evidence for the many theoretical causes of ASD.
Lead researcher, Professor Katrina Williams, said the problem clinicians frequently face when working with children with ASD is that there is no clear boundary between what behaviours are considered 'acceptable' versus being clinically significant. "Whilst it's simple for paediatricians and clinicians to identify children at the extreme ends of the spectrum, there is still this ambiguity for children who don't fit exactly into the criteria. This can lead to differences in the way it's interpreted and therefore differences in diagnosis."
"What is lacking are clear, well defined parameters or easy ways to assess what is normal at different ages, and for different genders and cultures. The identification of autistic behaviours is even more complex for children with intellectual disability or communication disorders. Despite many advances we do not know what 'good enough' social interaction is or what 'good enough' coping with change is and how this changes at different ages."
The overview found that from the first studies on ASD, the reported prevalence of ASD has increased from four in 10,000 to one in 100. However, researchers say whether the increase in reported prevalence of ASD means there has been a true increase in incidence or is due to awareness and broadening of diagnosis of ASD has been hotly debated.
While the researchers outline some factors that have been associated with autism in recent years, such as improved survival rate of premature babies, paternal age or antidepressant exposure, they say many have not been replicated in studies. One finding that has been recurring in studies is a connection with increasing maternal age.
However, if any or all of these associations were indeed a cause of autism the increase in prevalence that they would produce would be of a small magnitude, and so could not account for the large reported increases. Researchers say based on current evidence, it seems the reported increase in prevalence is not related to a true increase but rather related to other issues.
Researchers warn of the risks of adopting unproven theories about the cause of autism that have emerged during the decades when the increased prevalence has received a lot of attention, like vaccines, mercury, gut flora and cerebral inflammation, saying they have been 'rapidly translated to unproven interventions that have incurred direct and indirect costs to families and have put children at risk of adverse health outcomes. Examples of this are withholding immunisation, chemical castration and administration of chelation therapy, among others'.
Whilst there are no known causes for autism, researchers say it's time to give up on a single explanation for autism. The overview also highlights evidence for a genetic link to autism, with genetic abnormalities and new 'high risk' genes being found. It is also likely that gene-environment interactions will be found, given high rates of heritability but incomplete concordance of diagnosis amongst twins. Potential antenatal and perinatal environmental factors that increase or decrease the risk of ASD are still being explored and an explanation for the higher rates of ASD amongst males is still being sought.
Researchers say the lack of robust classification of autism along with limited high quality evidence base about its prevalence and possible causes leaves ample space for future discoveries.