Effectiveness of the Early Start Denver Model (ESDM) as an early intervention for young children with autism spectrum disorder in clinical settings in Japan: A non‐randomized controlled trial

Aim: The Early Start Denver Model (ESDM), a core Naturalistic Developmental Behavioral Intervention (NDBI), promotes developmental gains in young children with autism spectrum disorder (ASD) through socially embedded learning. Because high-intensity ESDM programs (approximately 20 h/week) are difficult to implement in many Japanese clinical settings, this study evaluated the effectiveness of a low-intensity ESDM program using standardized assessments. Methods: = 30) received 60-min ESDM sessions once weekly for 24 weeks, with parents present during sessions. Outcomes were assessed before and after intervention using the Autism Diagnostic Observation Schedule-2 (ADOS-2), Kyoto Scale of Psychological Development 2020 (KSPD-2020), and Vineland Adaptive Behavior Scales-II (Vineland-II). Results: = 0.0555). No significant between-group differences were found in the other outcome measures. Adaptive behavior showed modest increases in communication and socialization, although between-group differences were not statistically significant. Conclusion: Although the original ESDM recommends intensive delivery exceeding 15 h per week for 2 years, the present findings provide preliminary evidence that a low-intensity ESDM program-delivered once weekly for 24 sessions-can support meaningful developmental progress, even when changes in core autism symptoms are not detected after statistical adjustment in toddlers with ASD in Japanese clinical settings. These results highlight the feasibility of adapting ESDM principles to low-intensity service environments and underscore their potential applicability within Japanese cultural and systemic contexts.