Behavioral intervention is an evidence-based treatment for children with autism but there still exists some disagreement regarding how intensive the treatment needs to be. Little previous research has directly compared the effects of high to low-intensity behavioral intervention.

To compare the effects of high versus low-intensity behavioral intervention.

Compare outcomes in the area of diagnostic classification, intellectual functioning, executive functions, challenging behavior, language, socialization, and independent living skills after two years of treatment.

60 children with autism, under five years old, comprised two groups who received behavioral intervention services. The high-intensity group received 25–35 hours per week for two years and the low-intensity group received 8–15 hours per week of treatment. For all participants, a comprehensive battery of assessments was conducted prior to treatment and at annual intervals.

The high-intensity group outperformed the low-intensity group on all measures after two years of treatment.

This study provides further evidence that high intensity behavioral intervention produces greater gains than low-intensity treatment and the results suggest that children with autism under the age of five years should receive access to high-intensity treatment