Pervasive Developmental Disorder

A historical diagnostic category encompassing a group of neurodevelopmental conditions characterised by delays in socialisation, communication, and restricted patterns of behaviour. Under the DSM-IV, Pervasive Developmental Disorders included autism, Asperger syndrome, childhood disintegrative disorder, Rett syndrome, and PDD-NOS (Not Otherwise Specified). PDD-NOS was used for individuals who showed some but not all features of autism. In the DSM-5 (2013), these separate diagnoses were merged into the single category of Autism Spectrum Disorder (ASD), though the older terminology remains widely used in existing literature and by individuals who received their diagnosis under the previous system.