ASD (Autism Spectrum Disorders) and PDD (Pervasive Developmental Disorders) are often used interchangeably, but there are distinctions between the two terms. In the past, PDD was a broader diagnostic category that included several specific disorders, including autism. However, with the publication of the Diagnostic and Statistical Manual of Mental Disorders - Fifth Edition (DSM-5), the term PDD was replaced by ASD, which became the unifying term for all pervasive developmental disorders. Essentially, ASD is a more specific and up-to-date term that encompasses the various conditions that were previously classified under PDD.