The solitary RCT (where the intended comparison between randomized groups was actually carried out) in the 47-year history of ABA-based autism interventions--a small, largely failed study--is now drowned in an enormous murk of systematic, quasi-systematic, and not-systematic-at-all reviews. At this point in autism and autism advocacy history, no one should be surprised that this phenomenon encompasses dueling meta-analyses.
As with every other Verbatim, providing quotes doesn't mean I agree with them or the papers they are situated in. Here are quotes from the conclusions of three of the 2008 reviews:
Intervention studies suffer from methodological problems that preclude definitive conclusions regarding their efficacy. [...] While this review suggests that Lovaas may improve some core symptoms of ASD compared to special education, these findings are based on pooling outcomes from a few, methodologically weak studies with few participants and relatively short-term follow-up. [...] Future studies on the effectiveness of these interventions need to be more rigorous. (Ospina et al., 2008)
Given the few RCT studies, the few models that have been tested, and the large differences in interventions that are being published, it is clear that the field is still very early in the process of determining what kinds of interventions are most efficacious in early autism, the variables that mediate and moderate treatment effects, and the degree of both short-term and long-term improvement that can be expected for an individual child. (Rogers & Vismara, 2008)
Currently there is inadequate evidence that ABI [applied behavioral intervention] has better outcomes than standard care for children with autism. Appropriately powered clinical trials with broader outcomes are required. (Spreckley & Boyd, in press)
Ospina, M.B., Krebs Seida, J., Clark, B., Karkhaneh, M., Hartling, L., Tjosvold, L., Vandermeer, B., & Smith, V. (2008). Behavioural and developmental interventions for autism spectrum disorder: a clinical systematic review. PLoS ONE, 3:e3755.
Rogers, S.J., & Vismara, L.A. (2008). Evidence-based comprehensive treatments for early autism. Journal of Clinical Child and Adolescent Psychology, 37, 8-38.
Spreckley, M., & Boyd, R. (in press). Efficacy of applied behavioral intervention in preschool children with autism for improving cognitive, language, and adaptive behavior: A systematic review and meta-analysis. Journal of Pediatrics.