Vocabulary interventions for school-aged children with developmental language disorder : a systematic review and meta-analysis

Abstract

Objective: This systematic review evaluated the strength of evidence of vocabulary interventions on expressive oral language for school-aged children with Developmental Language Disorder (DLD). Methods: The protocol was pre-registered at Open Science Framework. Eight electronic databases were searched to identify experimental studies targeting children with DLD aged 5;0 to 12;0. Two independent reviewers critically appraised all included studies using the Joanna Briggs Institute Critical Appraisal Tools. Relevant results were synthesized with meta-analysis. Results: Thirty-eight studies relevant to the review’s research question were considered for inclusion; however, due to poor methodological features, only three studies were included (i.e. two randomized controlled trials and one single-subject experimental study). All studies had methodological and reporting flaws that reduced validity. The common outcome construct was expressive vocabulary. Data from 173 participants were included in meta-analysis. Results were inconclusive regarding the true effects of vocabulary interventions compared to a notreatment condition. A non-significant small effect size was generated (d = 0.36, p = 0.140). Conclusion: The strength of the evidence was inadequate to support the effectiveness of vocabulary interventions. Despite the numerous studies, the majority of studies had weak methodological quality. High-quality studies with good internal and external validity are required to support evidence-based practice.