Long-Term Outcomes of Early Intervention in 6-Year-Old Children with Autism

Background:  There is a lack of long-term outcomes studies for comprehensive autism interventions conducted with very young children. The only long-term outcome study of comprehensive autism intervention of which we are aware was published over 20 years ago (McEachin et al., 1993) and this seminal study was conducted with older children.  The Early Start Denver Model (ESDM) intervention, conducted for 2 years at 15 hours per week, begun when children were 18-30 months of age, showed evidence of efficacy immediately post-treatment in a randomized controlled trial (Dawson et al., 2010, 2012). The ESDM group significantly surpassed the community-intervention comparison group in IQ gain, adaptive behavior, and diagnostic changes.  Furthermore, an EEG study revealed normalized patterns in the ESDM group involving stronger responses to social than nonsocial stimuli, a pattern opposite that of the comparison group. 

Objectives:  We prospectively examine evidence for the sustained effects of early autism intervention, begun at 18-30 months of age, when children are 6 years of age. We also examine patterns of group differences in the ESDM group as compared with the Community-intervention group at 6 years of age. 

Methods:  Forty-five children completed the original outcome study.  Thirty-nine children were available for follow-up at 6 years of age (3 lost per group). During the two-year follow-up period the study no longer provided intervention to either group, so parents selected varying types and intensities of community-based interventions. Measures of IQ (Mullen, DAS), adaptive behavior (Vineland), autism symptoms (ADOS), and challenging behaviors (ABC) were gathered immediately post-intervention (age 4) and after the 2-year follow-up period (age 6).  Peer relations were assessed at age 6 (ADI-R, selected items.)    

Results:  The ESDM group, on average, maintained or increased improvements during the follow-up period in intellectual ability, adaptive behavior, symptom severity, and challenging behavior. At follow-up the ESDM group demonstrated improved core autism symptoms compared with the Community group. In contrast, no significant differences in core autism symptoms as assessed by the ADOS were found immediately post-treatment (see Dawson et al., 2010.)  In addition, the ESDM group had improved adaptive behavior and peer relations compared with the Community group at follow-up. The two groups did not differ in terms of intellectual functioning at age 6 follow-up.

Conclusions: These results indicate sustained and, in some domains, enhanced long-term effects of early ASD intervention. This is the first study to examine the role of early ESDM behavioral intervention initiated below 30 months of age in altering the longer term developmental course of autism.