Background

Historically, students with intellectual disability were not expected to learn to read, and thus were excluded from reading instruction. Over the past decades, societal expectations for this group of learners have changed in that children and adolescents with intellectual disability are now expected to be provided with, and benefit from, literacy instruction. This shift in societal expectations has also led to an increase in research examining effective interventions for increasing beginning reading skills for students with intellectual disability.

Objectives

To assess the effectiveness of interventions for teaching beginning reading skills to children and adolescents with intellectual disability.

Search methods

We searched the following electronic databases up to October 2019: CENTRAL; MEDLINE, including Epub Ahead of Print and In‐Process and Other Non‐Indexed Citations, Embase, 13 other databases, and two trials registers. We contacted authors of included studies, examined reference lists, and used Google Scholar to search for additional studies.

Selection criteria

We included randomized controlled trials (including trials that use quasi‐random methods of allocation such as date of birth), involving children and adolescents with intellectual disability (defined as an intelligence quotient (IQ) two standard deviations or more below the population mean) between the ages of 4 and 21 years, that evaluated the efficacy of a beginning reading intervention compared to a control intervention, including no treatment control, wait‐list control, treatment as usual, attention control, or alternate non‐reading instruction control.

Data collection and analysis

Two review authors independently screened titles and abstracts yielded by the search against the inclusion criteria, and extracted data from each trial using a piloted data extraction form to collect information about the population, intervention, randomization methods, blinding, sample size, outcome measures, follow‐up duration, attrition and handling of missing data, and methods of analysis. When data were missing, one review author contacted the study authors to request additional information. Two review authors assessed the risk of bias of each included study and rated the quality of the evidence using the GRADE approach (a systematic method for rating the certainty of evidence in meta‐analyses). We conducted random‐effect meta‐analyses, with inverse‐variance weighting to combine effect sizes for each of our primary and secondary outcomes. We presented effect sizes as standardized mean differences (SMD) with 95% confidence intervals (CI).

Main results

We identified seven studies involving 352 children and adolescents with intellectual disabilities that met the inclusion criteria. All studies provided the intervention in school settings. Four studies were conducted in the USA, one in Canada, and two in the UK. Three studies were funded by grants from the US Department of Education, Institute of Education Sciences; one study by the Canadian Language and Literacy Research Network and the Nova Scotia Health Research Foundation; and three studies did not indicate a funding source.

We identified some concerns with risk of bias, mainly due to the difficulty of blinding of participants and personnel, and the lack of blinding of outcome assessors.

Meta‐analyses of the data demonstrated small‐to‐moderate effects of beginning reading interventions delivered to children and adolescents with intellectual disability across four dependent variables. We found medium effect sizes in favor of the beginning reading interventions for the primary outcomes of phonologic awareness (SMD 0.55, 95% CI 0.23 to 0.86; 4 studies, 178 participants; moderate‐quality evidence), word reading (SMD 0.54, 95% CI 0.05 to 1.03; 5 studies, 220 participants; moderate‐quality evidence), and decoding (SMD 0.40, 95% CI 0.12 to 0.67; 5 studies, 230 participants; low‐quality evidence). The studies reported no adverse events. We also found a moderate effect for the secondary outcomes of oral reading fluency (SMD 0.65, 95% CI –0.12 to 1.42; 2 studies, 84 participants; low‐quality evidence) and language skills (SMD 0.28, 95% CI 0.03 to 0.54; 3 studies, 222 participants; moderate‐quality evidence).

Authors’ conclusions

Results from this review provide evidence that beginning reading interventions that include elements of phonologic awareness, letter sound instruction, and decoding, delivered to children and adolescents with intellectual disability, are associated with small‐to‐moderate improvements in phonologic awareness, word reading, decoding, expressive and receptive language, and oral reading fluency. These findings are aligned with previously conducted studies that examined the effects of reading interventions for people without intellectual disability.