What this study is
The 2010 Dawson et al. study is one of the most important pieces of autism intervention research of the past two decades. It was the first randomized controlled trial (RCT) — the gold standard of scientific evidence — to test intensive early intervention for toddlers with autism, specifically using the Early Start Denver Model (ESDM).
Prior research, including the landmark Lovaas (1987) study, had not used true random assignment. This study addressed that gap and produced compelling evidence that play-based, naturalistic early intervention can significantly improve language, cognition, and autism symptoms in very young children.
What is the Early Start Denver Model?
The Early Start Denver Model (ESDM) is an intervention approach developed by Dr. Geraldine Dawson and Dr. Sally Rogers. It combines principles from applied behavior analysis (ABA) with developmental and relationship-based approaches — delivering intensive intervention through play-based, child-led interactions rather than purely structured table sessions.
ESDM targets social communication, cognitive development, motor skills, and daily living skills simultaneously, embedded in activities that feel like natural play to the child.
What the researchers did
48 toddlers with autism, aged 18–30 months, were randomly assigned to one of two groups:
- ESDM group (24 children): Received 20 hours per week of ESDM therapy with trained therapists, plus 5+ hours per week of parent-delivered ESDM at home. Total: approximately 25 hours per week of structured intervention.
- Community treatment group (24 children): Received whatever services their families could access in the community — typically 9 hours per week on average of mixed therapy types.
The study ran for two years. Children were assessed at baseline and at the two-year endpoint on standardized measures of IQ, language, adaptive behavior, and autism symptoms.
What the researchers found
Children in the ESDM group showed significantly better outcomes across all primary measures:
- IQ: ESDM children gained an average of 17.6 IQ points over two years, compared to 7.0 points in the community group.
- Language: Significantly greater gains in receptive and expressive language in the ESDM group.
- Adaptive behavior: ESDM children showed improvements in daily living skills; community group showed declines.
- Autism symptoms: ESDM children showed greater reduction in autism symptom severity on the ADOS (Autism Diagnostic Observation Schedule).
- Diagnosis changes: A higher proportion of ESDM children received a less severe autism diagnosis at follow-up compared to the community group.
"Children who received ESDM showed significantly greater improvements in IQ, language, and adaptive behavior compared with children who received community intervention." — Dawson et al. (2010)
Why this study matters
Several features make this study particularly significant:
- It was a true RCT. Random assignment means the groups were equivalent at baseline, making the differences at follow-up much more convincingly attributable to the intervention.
- The participants were very young. Starting at 18–30 months targets the critical early window of brain plasticity when intervention has the greatest potential impact.
- It validated a naturalistic approach. ESDM is more child-led and play-based than traditional ABA — this study showed that play-based intervention can produce outcomes comparable to or exceeding more structured approaches.
- Parent implementation was built in. Parents were trained to deliver ESDM at home, and this was a core component of the intervention — not an add-on.
What it means for parents
This study reinforces several important messages for parents:
- Starting intervention early — as young as 18 months — produces meaningful benefits. If you have concerns about your child's development, act quickly.
- Play-based learning is not just entertaining — when structured around clear developmental targets, it is a powerful vehicle for skill development.
- Parent-implemented intervention is not just a supplement — in this study, parent delivery was a core component of the most effective treatment arm.
- Consistency and intensity matter. 25 hours per week outperformed 9 hours per week significantly. While most families can't replicate 25 hours of professional therapy, maximizing consistent, structured practice at home makes a meaningful difference.
Limitations
- The community treatment group received less total intervention hours (9 vs. 25), making it difficult to separate the effect of ESDM specifically from the effect of more hours of any structured intervention.
- The sample size (48 children) is relatively small for an RCT, though effect sizes were large enough to reach significance.
- ESDM requires trained therapists to deliver the therapist portion — it is not purely a parent-implemented approach.
Full citation
Dawson, G., Rogers, S., Munson, J., Smith, M., Winter, J., Greenson, J., Donaldson, A., & Varley, J. (2010). Randomized, controlled trial of an intervention for toddlers with autism: The Early Start Denver Model. Pediatrics, 125(1), e17–e23. https://doi.org/10.1542/peds.2009-0958