The recent reframing of autism spectrum disorder (ASD) guidelines could likely see the reduction of autism diagnoses by up to a third, says a study from the Columbia School of Nursing.

The American Psychiatric Association (APA) updated the definitions of what constitutes autism in 2013, though findings from the Columbia study suggest that the reworked guidelines will deprive developmentally delayed children of certain assistive measures, such as social and clinical support.

The fifth edition of the APA's Diagnostic and Statistical Manual of Mental Disorders, known as DSM-5, has removed three key sub-groups previously recognized as part of the broader family of autism spectrum disorders. Autistic disorder (AD), Asperger's disorder and pervasive development disorder-not otherwise specified (PDD-NOS) have effectively been erased from DSM-5, while remaining guidelines are restricted in diagnostic scope.

The study, titled How Will DSM-5 Affect Autism Diagnosis? A Systematic Literature Review and Meta-analysis and published in the Journal of Autism and Developmental Disorders, unearthed a 31 percent reduction in the number of autism diagnoses since DSM-5 came into effect, in contrast to guidelines from the manual's prior iteration, DSM-IV-TR. The study also reported findings of a 22% decrease in incidence of diagnosis of AD, as well as a 70% decrease in PDD-NOS diagnoses.

The study's leader, Kristine M. Kulage, pointed to certain vulnerabilities that children previously on the autism spectrum would experience. "This study raises a concern that a medical provider diagnosing a child under the new guidelines won't find the child to be on the autism spectrum, when the same child under the old criteria might have been diagnosed with ASD," she said. "We are potentially going to lose diagnosis and treatment for some of the most vulnerable kids who have developmental delays. In many instances, children require a diagnosis of ASD to receive medical benefits, educational support and social services."

The Centers for Disease Control and Prevention estimate that 1 in 88 children in the United States suffer from ASD, though Kulage and her team argue that this figure will change in light of the DSM-5 update. The study also illustrates that the implementation of ASD guidelines is as much a policy move as it is a medical best practice, and suggests further research around undiagnosed individuals who may, nevertheless, require support.