Objective

We prospectively examined evidence for the sustained effects of early intervention based on a follow-up study of 39 children with ASD who began participation in a randomized clinical trial testing the effectiveness of the Early Start Denver Model (ESDM) at age 18 to 30 months. The intervention, conducted at a high level of intensity in-home for 2 years, showed evidence of efficacy immediately posttreatment.

Method

This group of children was assessed at age 6 years, 2 years after the intervention ended, across multiple domains of functioning by clinicians naive to previous intervention group status.

Results

The ESDM group, on average, maintained gains made in early intervention during the 2-year follow-up period in overall intellectual ability, adaptive behavior, symptom severity, and challenging behavior. No group differences in core autism symptoms were found immediately posttreatment; however, 2 years later, the ESDM group demonstrated improved core autism symptoms and adaptive behavior as compared with the community-intervention-as-usual (COM) group. The 2 groups were not significantly different in terms of intellectual functioning at age 6 years. Both groups received equivalent intervention hours during the original study, but the ESDM group received fewer hours during the follow-up period.

Conclusion

These results provide evidence that gains from early intensive intervention are maintained 2 years later. Notably, core autism symptoms improved in the ESDM group over the follow-up period relative to the COM group. This improvement occurred at the same time that the ESDM group received significantly fewer services. This is the first study to examine the role of early ESDM behavioral intervention initiated at less than 30 months of age in altering the longer-term developmental course of autism.

This study aimed to provide initial validity and reliability of the Measure of NDBI Strategy Implementation-Caregiver Change (MONSI-CC), a novel measure that captures changes in caregivers' implementation of NDBI strategies during early intervention. The MONSI-CC was applied to 119 observations of 43 caregiver-child dyads of preschoolers with autism spectrum disorders (ASD). The MONSI-CC showed high inter-rater and test-retest reliability and captured significant improvements in caregivers' implementation of NDBI strategies. Significant associations between improvements in caregiver NDBI implementation and improvements in the child's ASD symptoms also emerged. Our work shows promising evidence for the utility of the MONSI-CC to evaluate implementation of NDBI strategies by caregivers as a mediating and moderating factor for treatment effects on children with ASD.