Regression versus no regression in the autistic disorder: developmental trajectories.

Heslop et al. (2007) watched two groups of preschoolers with autism. One group lost skills they once had. The other group never lost skills.

They tracked language, play, and communication every year from age two to six.

Kids who never regained moved ahead faster. Their words, play, and back-and-forth talk grew more each year.

Kids who had lost skills earlier stayed behind in the same areas.

Boterberg et al. (2019) later saw the same split. They added that regressed children also show more repetitive play and rigid routines in grade school.

Hu et al. (2024) gave both groups one year of ABA. Young non-regressed kids made big jumps. Young regressed kids made only small jumps. The pattern fits: the gap seen by P et al. is hard to close even with treatment.

Tan et al. (2021) pooled 75 studies and found about one in three children with autism lose skills. That number places the regressed group in P et al. inside a common subtype, not a rare edge case.

Screen early for any loss of words, gestures, or play. If you see it, plan denser teaching hours and add parent coaching. Track both groups separately in your data. Expect slower progress for the regressed cluster and celebrate small wins to keep families engaged.