The earlier the better: An RCT of treatment timing effects for toddlers on the autism spectrum
Authors: Guthrie Whitney , Wetherby Amy M , Woods Juliann , Schatschneider Christopher , Holland Renee D , Morgan Lindee , Lord Catherine E 
Published: March 2023

Robust evidence supports the efficacy of early autism intervention. Despite broad consensus that earlier intervention leads to better outcomes, evidence for this has been limited to correlational studies. This study examined timing effects of the Early Social Interaction (ESI) model, a parent-implemented intervention, using a complete crossover randomized controlled trial (RCT). Effects of Individual-ESI were compared when initiated at 18 or 27 months of age, and also contrasted with effects of the less intensive Group-ESI as an active control condition. Participants included 82 autistic toddlers who received 9 months of Individual-ESI and 9 months of Group-ESI, with the timing/order randomized. Blinded clinicians completed assessments at baseline (18 months of age), end of Condition 1 (27 months), and end of Condition 2 (36 months). Toddlers randomized to Individual-ESI at 18 months showed greater gains during treatment than those starting Individual-ESI at 27 months in receptive/expressive language, social communication, and daily living skills. This pattern was not observed for Group-ESI, demonstrating that timing effects were specific to Individual-ESI and ruling out maturation effects. This RCT demonstrated that earlier intensive, individualized intervention led to greater improvements, and suggests that even a narrow window of 18 versus 27 months may impact child outcomes. Lay abstract Behavioral interventions that incorporate naturalistic, developmental strategies have been shown to improve outcomes for young children who receive an autism spectrum disorder (ASD) diagnosis. Although there is broad consensus that children on the spectrum should begin supports as soon as possible, the empirical evidence for this is relatively limited and little is known about the optimal age to start autism-specific interventions. Our team conducted a randomized controlled trial (RCT) to test the effects of starting intervention at different ages, using the Early Social Interaction (ESI) model, a parent-implemented intervention for toddlers on the spectrum. Participants included 82 autistic toddlers and their caregiver(s) who received 9 months of Individual-ESI and 9 months of Group-ESI, with the timing/order of these two treatment conditions randomized. Thus, families received the more intensive and individualized Individual-ESI at either 18 or 27 months of age. Results revealed that children who received Individual-ESI earlier showed greater treatment gains than those who received this intervention later. Gains were demonstrated in several areas, which included the use and understanding of language, social use of communication skills, and self-help skills. Importantly, these findings were specific to the intensive and individualized parent coaching model compared to group-based treatment, allowing us to rule out the possibility that these timing effects were due to children getting older rather than the treatment itself. Our results suggest that even a narrow window of 18 versus 27 months may have an impact on outcomes and underscore the importance of screening and evaluation as young as possible.