Adoption and cognitive development: a meta-analytic comparison of adopted and nonadopted children’s IQ and school performance

Centre for Child and Family Studies, Leiden University, Leiden, Netherlands.
Psychological Bulletin (Impact Factor: 14.39). 04/2005; 131(2):301-16. DOI: 10.1037/0033-2909.131.2.301
Source: PubMed

ABSTRACT This meta-analysis of 62 studies (N=17,767 adopted children) examined whether the cognitive development of adopted children differed from that of (a) children who remained in institutional care or in the birth family and (b) their current (environmental) nonadopted siblings or peers. Adopted children scored higher on IQ tests than their nonadopted siblings or peers who stayed behind, and their school performance was better. Adopted children did not differ from their nonadopted environmental peers or siblings in IQ, but their school performance and language abilities lagged behind, and more adopted children developed learning problems. Taken together, the meta-analyses document the positive impact of adoption on the children's cognitive development and their remarkably normal cognitive competence but delayed school performance.

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Available from: Marinus H. van IJzendoorn, Jul 25, 2015
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    • "In all cases the mother was the primary caregiver (for more details see Stams, Juffer, & Van IJzendoorn, 2002). When their children were between 6 and 9 months of age, 26 of them were part of a randomly selected group of 50 families that received a short-term intervention aimed at promoting maternal sensitivity (Juffer, Bakermans-Kranenburg, & Van IJzendoorn, 2005). "
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    • "Some publications reported prevalence rates for several types of maltreatment for the same samples, resulting in an overlap between samples. We therefore used 85 per cent CIs as a conservative way of testing whether the prevalences of SA, PA, EA, PN and EN were statistically significantly different (Van IJzendoorn et al., 2005). Non-overlapping 85 per cent CIs suggest a significant difference between combined effect sizes (Goldstein and Healy, 1995). "
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    • "When moderator categories' effect sizes were not independently calculated (i.e., different categories contained different outcomes obtained from the same participants), the 85% confidence intervals surrounding the calculated average effect sizes were compared as an exploratory test of whether effect sizes significantly differed from one another. An absence of overlap between 85% confidence intervals was considered a statistically significant difference under a random effects model (Goldstein & Healy, 1995; Van IJzendoorn, Juffer, & Poelhuis, 2005). To allow for reliable estimates of meta-analyzed effect sizes, we required a minimum of four studies per moderator category (Bakermans-Kranenburg, Van IJzendoorn, & Juffer, 2003). "
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