We have identified nine studies of LEAP published in English-language, peer-reviewed journals. These studies included more than 500 autistic children aged from three to five, although the majority of these children came from just two studies (Strain and Bovey, 2011 with 294 participants; Boyd et al, 2014 with 198 participants).
The study by Strain and Bovey (2011) compared two versions of LEAP with each other: the full-scale LEAP replication training or a comparison condition in which staff were provided with LEAP intervention manuals and related written materials only. It included 294 pre-school children and was conducted in 56 classrooms in seven different states within the US. It reported that the children who received the full version of LEAP were found to have made significantly greater improvement than the other group on measures of cognitive, language, social, and problem behaviour, and autism symptoms.
The study by Boyd et al (2014) compared LEAP with TEACCH and with non-model specific practices (standard teaching). It included 198 pre-school children and was conducted in 74 different classrooms in four different states within the US. It reported that each of the three interventions produced significant benefits such as improvements in autism characteristics and severity, communication skills and reciprocal social interactions. None of the three interventions produced any changes in sensory and repetitive behaviours.The other studies all looked at various early versions of LEAP and all of them reported gains in areas such as social communication skills.