Why is this review important?
Intellectual disability is defined as an intelligence quotient (IQ) of two standard deviations or more below the population mean, or an IQ score below 70. 
Intellectual disability affects functioning in two areas: cognitive (learning, problem solving, judgement) and adaptive (activities of independent living). Intellectual disability affects about 1% of the population, and about 85% of those have a mild level of disability. 
Literacy (learning to read or write), an essential skill in today’s world, is one of the intellectual skills that gets more commonly affected. Beliefs have changed to recognize that to achieve inclusion for pupils with special needs, it is important to remediate and facilitate their reading skills.
Intellectual disability includes a heterogeneous group of disorders with wide range and variation in skills development. Reading and comprehension skills correlate to oral language ability, phonemic awareness, phonological processing, working memory, executive function, and inferential reasoning. It is vital to understand these influencing and modulating factors for planning optimal training programs where evidence-based practice would help. 
This Cochrane systematic review reveals the effectiveness of such an intervention program that would guide clinical practice, teaching style, and future research.
Who is interested in this review?
Parents, loved ones, and caregivers of persons with intellectual disabilities; professionals dealing with intellectual impairments; professionals working with cognitive disorders and intellectual disabilities; general practitioners; researchers working on such impairments; and policymakers.
What is the aim of this review and what is it about?
The objective was to assess the effectiveness of interventions for reading-skills learning in children and adolescents with intellectual disability. The review data included 7 randomized trials (RCTs) published before October 2019 and conducted in the U.S., Canada, and the U.K. Funding sources were declared in only 4 studies. 
These studies involved 352 children and adolescents ages 4–21 with intellectual disability, and they compared a reading training group with a control group (with no treatment, wait-list, alternate non-reading instruction, or treatment only for attention). Intervention targets were letter-sound awareness (phonological awareness and phonics), blending sounds into words (semantics encoding), reading words (lexical processing), correctly pronouncing written words (decoding), and vocabulary building (language skill). Interventional methods consisted of sight words and phonics, where reading techniques used are (a) direct, explicit instructions; (b) modelling; (c) practicing; (d) automaticity or fluency; (e) systematic prompting and fading; (f) corrective feedback; and (g) scaffolding. Different factors affecting reading skill development also are discussed in this review.
What does evidence from the review tell us?
The review evaluated primary outcomes of phonologic awareness, word reading, decoding, adverse events, and secondary outcomes of oral reading fluency and language skills. The evidence analysed was (i) low-to-moderate effects on beginning skill of reading; (ii) moderate effect on phonologic awareness, oral-reading-fluency, and language-skills; and (iii) low evidence on decoding. None of the studies reported any side effects. Authors reported risk of bias in the studies, mainly due to non-blinded participants and/or trainers and non-blinded outcomes assessors.
Author’s conclusion of the review
Results from this review provide evidence that beginning reading interventions 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 previous studies that examined the effects of reading interventions for people without intellectual disability.
What should be done next?
Quality of evidence is low to moderate due to the small number of studies and small number of participants (small sample size). Future experimental studies focusing on beginning reading skill with a bigger sample, blinded (for intervention outcomes), targeting “multi-component reading intervention” and elaborating on study duration, intervention intensity, language orthography (opaque like English), and broader age range/age segregation (preschool, elementary school, adolescents, young adults, etc.) are needed. Such studies would increase the ability of practitioners to optimize reading outcomes for a broader segment of the population with intellectual disability. 

Comment by Sunita Gudwani