Parental differential treatment of siblings linked with internalizing and externalizing behavior: A meta-analysis.

This meta-analysis linked relative and absolute parental differential treatment (PDT) with internalizing and externalizing behavior of children and adolescents. Multilevel meta-analysis data represented 26,451 participants based on 2890 effect sizes coming from 88 sources, nested within 43 samples. Participants were between 3.18 and 18.99 years of age (M age  = 12.64, SD = 3.89; 51.31% female; 82.23% White; 54.68% from the United States). Less-favored treatment (relative PDT) was linked to more internalizing and externalizing behavior. Additionally, greater differences in parenting between siblings (absolute PDT) were linked to more internalizing and externalizing behavior. Some links were moderated by other factors. For example, some effects were stronger when PDT was reported by children, and others, when siblings were closer in age.