Language disorder is a cardinal challenge for children with Down syndrome, and their learning capacity has been debated. The aim of the current study was to conduct a systematic review and meta-analysis of existing language interventions for children with Down syndrome to reveal knowledge about the effects of these interventions and identify any common characteristics specific to effective or ineffective interventions. A systematic search was conducted in databases relevant for education, speech and language therapy, and psychology. Based on a set of predefined inclusion criteria, the hits were screened and coded. Eight studies were synthesised in a systematic review and four in a meta-analysis. The overall effect of the interventions was large (g = 1.01), but significant transfer effects to untrained aspects of language were rarely found. Interventions showing significant effects varied with regards to numerous characteristics including the age of the target group, the intervention approach, the dosage, and the implementer. The common characteristic across the effective interventions was simply the aim of improving language skills in children with Down syndrome. Overall, there was a moderate to high risk of bias across all studies. To conclude, children with Down syndrome have the potential to respond to language intervention. However, more interventions that reach transfer effects are needed to maximise children's language outcomes. Based on the limited number of studies and a moderate to high risk of bias across the studies, there is a great need for more robust intervention studies to ensure that future interventions are informed by high-quality research.
Keywords: Down syndrome; Evidence-Based practice; Intervention; Language; Trisomy 21.
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