Forty Years of Reading Intervention Research for Elementary Students with or at Risk for Dyslexia: A Systematic Review and Meta-Analysis

This meta-analysis included experimental or quasi-experimental intervention studies conducted between 1980 and 2020 that aimed to improve reading outcomes for Grade K-5 students with or at risk for dyslexia (i.e., students with or at risk for word reading difficulties, defined as scoring at or below norm-referenced screening or mean baseline performance thresholds articulated in our inclusion criteria). In all, 53 studies reported in 52 publications met inclusion criteria (m = 351; total student N = 6,053). We employed robust variance estimation to address dependent effect sizes arising from multiple outcomes and comparisons within studies. Results indicated a statistically significant main effect of instruction on norm-referenced reading outcomes (g = 0.33; p < .001). Because there was significant heterogeneity in effect sizes across studies (p < .01), we used meta-regression to identify the degree to which student characteristics (i.e., grade level), intervention characteristics (i.e., dosage, instructional components, multisensory nature, instructional group size), reading outcome domain (i.e., phonological awareness, word reading/spelling, passage reading, or reading comprehension), or research methods (i.e., sample size, study design) influenced intervention effects. Dosage and reading outcome domain were the only variables that significantly moderated intervention effects (p = .040 and p = .024, respectively), with higher dosage studies associated with larger effects (b = 0.002) and reading comprehension outcomes associated with smaller effects than word reading/spelling outcomes (b = -0.080).