Brief report: pervasive developmental disorder can evolve into ADHD: case illustrations.

Fein et al. (2005) followed a small group of young children. Each child first received a pervasive developmental disorder (PDD) diagnosis.

By elementary school the same kids met full criteria for attention-deficit/hyperactivity disorder (ADHD). The authors present case stories to show the switch.

The children's early autism-like features faded. Hyperactivity, impulsivity, and attention problems moved to the front.

Clinicians changed the primary label from PDD to ADHD. The shift happened between early and middle childhood.

Hong et al. (2021) looked at 979 preschoolers with ASD. Fifty-seven percent already showed moderate-to-high ADHD symptoms. The two studies seem to clash: one says ASD can turn into ADHD, the other says ADHD signs sit inside ASD from the start. The gap is timing. Deborah et al. track a later, full diagnostic swap, while S et al. capture early overlap.

Gadow et al. (2006) mapped DSM-IV ADHD subtypes onto children with PDD. They found the subtypes work the same way in both groups. This supports the target paper: if the subtypes fit, an ADHD diagnosis after PDD is valid.

Ohan et al. (2015) showed that kids who carry both ASD and ADHD labels have lower adaptive skills than ADHD-only peers. They extend the target finding by showing the real-world cost after the diagnostic change.

Labels can move. A child you see for stereotypy at age four may return at age eight for calling out and leaving his seat. Plan reassessment every few years. Update treatment goals when the primary diagnosis shifts from ASD to ADHD or vice versa. Share this possibility with parents early so they expect evolution, not failure of the first label.