Intensive behavior therapy in toddlers with autism can yield significant progress and even result in an improved diagnosis, first-of-its-kind research indicates.

While behavior therapy is standard protocol for older children with autism, the study published online Monday in Pediatrics is the first to show that children as young as 18 months can benefit.

Researchers looked at a technique called the Early Start Denver model, which utilizes applied behavior analysis combined with a relationship-based approach. Half of the 48 children in the study received two years of the intense therapy 25 hours per week provided by therapists and their parents who were trained in the method. Meanwhile, the remainder of the children were referred to traditional community programs.

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At the end of the two-year period, there were striking differences in IQ between children in the two groups even though they began at the same level. On average, the children who received the intense therapy experienced an 18 point increase in IQ while children in the community group improved by about four points. There were also more significant gains in listening and understanding skills among the group that used the Early Start Denver model.

Ultimately, seven children in the more intensive therapy group received a new, milder diagnosis of pervasive developmental disorder not otherwise specified instead of autism. Just one child who received the community treatment had an improved diagnosis.

“Parental involvement and use of these strategies at home during routine and daily activities are likely important ingredients of the success of the outcomes and their child’s progress. The study strongly affirms the positive outcomes of early intervention and the need for the earliest possible start,” says Geraldine Dawson, chief science officer at Autism Speaks and the lead author of the study.