A five-year study involving 48 diverse, 18- to 30-month-old children with autism and no other health problems has found a novel early intervention program to be effective for improving IQ, language ability, and social interaction. The Early Start Denver Model combines applied behavioral analysis (ABA) teaching methods with play-based routines that focused on building a relationship with the child. Half the children received two two-hour sessions five days a week from specialists (but in their own homes) plus five hours a week of parent-delivered therapy. The remaining children were referred to community-based programs. After two years, the IQs of the children in the intervention group had improved by an average of around 18 points, compared to a little more than four points in the comparison group. The intervention group also had a nearly 18-point improvement in receptive language (listening and understanding) compared to around10 points in the comparison group. Seven of the children in the intervention group received an improved diagnosis from autism to the milder condition known as 'pervasive developmental disorder not otherwise specified' (PDD-NOS), compared to only one child in the community-based therapy group.
Early intervention for toddlers with autism highly effective
 Randomized, Controlled Trial of an Intervention for Toddlers With Autism: The Early Start Denver Model. Pediatrics. 125(1), e17-23 - e17-23.(2010).