Final answer:
The DSM-5 no longer lists Asperger's syndrome, Childhood Disintegrative Disorder, and Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS) as separate diagnoses; they are now included under Autism Spectrum Disorder (ASD).
Step-by-step explanation:
In the transition from the DSM-IV to the DSM-5, certain disorders that were previously categorized separately under the umbrella of Pervasive Developmental Disorders (PDD) are no longer listed individually. Notably, the DSM-5 has merged several diagnoses into the broader category of Autism Spectrum Disorder (ASD). The most significant change is that Asperger's syndrome, which was once considered a distinct disorder, is now subsumed under ASD.
This integration reflects an understanding that autism represents a spectrum of related conditions with varying degrees of symptoms and functional levels rather than distinct disorders. Additionally, other disorders such as Childhood Disintegrative Disorder and Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS) have also been absorbed into the ASD classification.