2021
DOI: 10.3758/s13428-021-01549-x
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Dyslexia treatment studies: A systematic review and suggestions on testing treatment efficacy with small effects and small samples

Abstract: Poor response to treatment is a defining characteristic of reading disorder. In the present systematic review and meta-analysis, we found that the overall average effect size for treatment efficacy was modest, with a mean standardized difference of 0.38. Small true effects, combined with the difficulty to recruit large samples, seriously challenge researchers planning to test treatment efficacy in dyslexia and potentially in other learning disorders. Nonetheless, most published studies claim effectiveness, gen… Show more

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Cited by 22 publications
(19 citation statements)
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“…The consequence of this aspect is that randomized controlled studies are infrequent and to this is added the difficulty of collecting data over time (follow-up). It follows that, as in the present study, the effects in this field are small [ 64 ]. Therefore, another limitation of this study is the small, heterogeneous, in terms of different learning disabilities, sample with the consequence that the results cannot be extended to the entire population of patients with SLD.…”
Section: Discussionsupporting
confidence: 63%
“…The consequence of this aspect is that randomized controlled studies are infrequent and to this is added the difficulty of collecting data over time (follow-up). It follows that, as in the present study, the effects in this field are small [ 64 ]. Therefore, another limitation of this study is the small, heterogeneous, in terms of different learning disabilities, sample with the consequence that the results cannot be extended to the entire population of patients with SLD.…”
Section: Discussionsupporting
confidence: 63%
“…Given its functional impairment and impact on learning, DD is recognized as a risk factor for reduced socio-economic outcomes (Carroll et al, 2005;Aro et al, 2019) and the onset of emotional-behavioral difficulties (Hendren et al, 2018;de Lima et al, 2020;Wang, 2021;Xiao et al, 2022). Although some treatments, especially those based on phonics, have shown some efficacy in improving reading skills in children and adolescents with DD (Galuschka et al, 2014;McArthur et al, 2018;Wanzek et al, 2018), there is still some variability in response and treatments are not effective for all children (Gabrieli, 2009;Toffalini et al, 2021). These reasons drive the need to provide further testing and validation of treatments in DD.…”
Section: Introductionmentioning
confidence: 99%
“…The overall heterogeneity was modest. As explained above, we adopted the simulation procedure and code offered by Toffalini et al (2021) to perform power analysis for a pre‐test/post‐test‐control design. All simulations were run with 5000 iterations, assuming test/re‐test stability of r = 0.70 and a critical α = 0.05 for statistical significance.…”
Section: Resultsmentioning
confidence: 99%
“…However, for the most likely true effect size, d = 0.27, 80% power is achieved with N = 220 (i.e., n = 110 per group). Nonetheless, power could be increased even with the same sample size, using repeated measurements for each time point and/or using measures with higher reliability (seeToffalini et al, 2021).Across the studies/group comparisons included in our metaanalysis, the median sample size was N = 43 (about n = 22 per group).None of the group comparisons would reach the required level of power for d = 0.27, as indicated above (the largest sample size for a single group comparison was 200, including 99 treated individuals and 101 controls). Considering the median sample size of 43 (i.e., n = 22 per group), the median power of the studies that we reviewed could be estimated at 22% for d = 0.27; considering the uncertainty bounds, it could be estimated at 10% for d = 0.15 to 39% for d = 0.38.…”
mentioning
confidence: 99%