The Siblings of Individuals with Mental Retardation: A Quantitative Integration of the Literature

The sibling relationship has recently become the focus of much research in developmental psychology. The family system perspective implies the presence of a sibling with mental retardation will impact on the psychological development and functioning of their typically developing siblings. Past reviews of the literature have found this impact to be negative but there is the suggestion of positive consequences to having a sibling with mental retardation. The present meta-analysis sought to quantitatively integrate 25 studies and 79 effect sizes from the literature on the siblings of individuals with mental retardation. A small negative effect for having a sibling with mental retardation was discovered that could not be attributed to a publication bias or some other artifact. This negative effect was greatest for direct observation measures, measures of psychological functioning, especially depression, and for children. Limitations to this meta-analysis and directions for future research are discussed.