Eligible studies needed to include an early intensive behavioural intervention (EIBI) based on the University of California at Los Angeles (UCLA) Young Autism Project model. Participants needed to have a diagnosis of autistic disorder, autism spectrum disorder (ASD), pervasive development disorder (PDD) or pervasive developmental disorder not otherwise specified (PDD-NOS). Participants had to have a mean chronological age of less than 84 months at the beginning of treatment. Mean duration of EIBI should be greater than or equal to 12 months and at least one child outcome should be reported. Studies needed to be of an experimental or quasi-experimental design.
Half of the studies focused on participants with autism and half included participants with allied diagnoses. Most of the children were less than 42 months old. There was a wide range of mean IQ scores (28 to 83). Differences existed in all characteristics of intervention across studies (including intensity, duration, organisational, personnel and setting). The range of the total number of hours of therapy was 774 to 7,793. Across the comparative studies, comparators included: different intensities of behavioural intervention; other treatments such as treatment as usual, eclectic treatment and specialist nursery schools; and different service coordination models. Where reported, some studies reported that greater than 80% of the participants received supplemental treatments.
The authors stated neither how studies were selected for the review nor how many reviewers performed the selection.