Why were Asperger syndrome and classic autism folded into one autism spectrum disorder diagnosis?

In 2013, the publication of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) led to the consolidation of several previously distinct conditions—including classic autism, Asperger syndrome, and pervasive developmental disorder not otherwise specified—into a single umbrella diagnosis of autism spectrum disorder (ASD).123

This change was made to better reflect the scientific understanding that these conditions represent a continuum of symptoms rather than entirely separate disorders. By grouping them under one diagnosis, clinicians can now distinguish individuals based on the severity of their core symptoms—specifically deficits in social communication and the intensity of repetitive behaviors or restricted interests—and the level of daily support they require. While the formal diagnostic category has changed, some individuals previously diagnosed with Asperger syndrome may still choose to use that term to describe their personal experience.134