The earlier the better: An RCT of treatment timing effects for toddlers on the autism spectrum
Starting parent-led Early Social Interaction at 18 months beats waiting until 27 months on every key skill.
01Research in Context
What this study did
Guthrie et al. (2023) randomly assigned autistic toddlers to start parent-led Early Social Interaction at 18 months or 27 months.
Parents learned to coach their child at home during daily play and routines.
The team tracked language, social, and daily-living skills for both groups.
What they found
Kids who began at 18 months scored higher in language, social communication, and daily living skills.
The nine-month head start created a clear, lasting edge.
Earlier truly is better when parents are the therapists.
How this fits with other research
Giallo et al. (2014) and Vivanti et al. (2016) already saw bigger gains when toddlers began EIBI or ESDM before age 2.
Guthrie’s RCT now proves the link is causal, not just a coincidence.
Eikeseth et al. (2007) shows ABA still helps if you wait until 4-7 years, but the boost is smaller.
Together the papers draw a curve: start before 2 for the biggest win, start later if you must, but every month counts.
Why it matters
You can tell funders and families that losing nine months costs real skills, not just time.
Push hard for evaluations at 18 months and train parents the same week.
Use Guthrie’s home-coaching scripts to keep the program low-cost and parent-friendly.
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02At a glance
03Original abstract
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. 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.
Autism, 2023 · doi:10.1177/13623613231159153