Intervention Studies with Group Design Targeting Expressive Phonology for Children with Developmental Speech and Language Disorder: A Systematic Review and Meta-Analysis

Background: Phonological difficulties are prevalent in children with speech and/or language disorders and may hamper their later language outcomes and academic achievements. These children often form a significant proportion of speech and language therapists' caseloads. There is a shortage of information on evidence-based interventions for improving phonological skills in children and adolescents with speech and language disorder. Aims: The aim of this systematic literature review and meta-analysis was to systematically examine the effects of different intervention approaches on speech production accuracy and phonological representation skills in children with speech and language disorders. Methods: A preregistered systematic review (International Prospective Register of Systematic Reviews ID: CRD42017076075) adhering to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was completed. Seven electronic databases (PubMed, Web of Science, ERIC, PsychINFO, Cochrane Library, SCOPUS and Linguistics & Language Behavior Abstracts) were searched for studies related to oral language interventions with children with developmental speech and/or language disorder (mean age ranging from 3-18 years) published between January 2006 and August 2022. The included articles reported intervention studies with a group design in which speech production accuracy was the outcome measure. Studies were appraised using the Cochrane risk of bias tool, and individual effect sizes were calculated using standardised means differences when enough data was available. A meta-analysis was conducted obtaining the average standardised mean difference d. Heterogeneity, influence of possible moderator variables and publication bias were explored. Results: The 23 studies that met the inclusion criteria presented low-medium risk of bias. Nine effect sizes were obtained from seven of these studies that presented a pre-post-test with a control group design. Medium-high average effect sizes were found in phonological accuracy. Heterogeneity was found between individual effect sizes. Significant moderator variables and publication bias were not detected. Conclusions: The results of this meta-analysis indicate positive effects on speech production accuracy. Based on this review, further improvements in the quality of reporting for intervention research are required in developing the evidence base for practice.