Early developmental trajectories associated with different styles and intensities of ESDM-based community intervention

Background: The Early Start Denver Model (ESDM) is a naturalistic developmental behavioral intervention (NDBI) widely used to support early development in young autistic children. This study examines early developmental trajectories associated with different styles and intensities of ESDM-based intervention compared with community Therapy as Usual (TAU) over a 6-month period. It also explores predictors of individual language development based on the intervention style. Methods: A total of 112 autistic children participated in the study and were assessed longitudinally while receiving either higher (6 h a week) or lower (3 h a week) intensity ESDM, or TAU at higher (6 h a week) intensity (N = 29, 32, and 51 participants in each group, respectively). Results: The primary findings show that children receiving higher-intensity ESDM exhibited steeper developmental trajectories than children receiving TAU in all the developmental areas such as Language, Personal-Social skills, Performance, Eye-Hand coordination and the General score. Notably, lower-intensity ESDM was associated with steeper developmental gains in individual general development, language, personal social skills, and performance when compared to TAU at double the intensity. Additionally, secondary results indicate that language developmental trajectories are influenced by different factors in the ESDM and TAU groups, with social domain and adaptive behaviors predicting language progress in the ESDM group and baseline cognitive skills predicting language development in the TAU group. Conclusions: This study provides observational evidence that different intervention models and intensities may be associated with different short-term developmental trajectories in community settings, particularly where only limited weekly intervention hours are feasible. These findings may help inform service planning in low-resource contexts, while requiring replication in more controlled designs. Trial registration: Clinical Trial ID: NCT06494605.