Parental Differential Warmth, Hostility, and Sibling Differences in Internalizing and Externalizing Behavior Problems: A Meta-Analysis

Parental differential treatment (PDT) of siblings is associated with differences in children's behavioral adjustment. The current meta-analysis examined the extent to which associations between relative PDT and sibling differences in behavior problems differ by type of parenting behavior (i.e., differential hostility vs. differential warmth) and type of behavior problems (i.e., differential externalizing vs. internalizing behavior problems). In September 2021, we systematically searched APA PsycInfo and Web of Science, yielding 2,259 unique hits with 19 eligible publications reporting on 215 effect sizes from 13 unique samples. The overall association between relative PDT (i.e., receiving less warmth and more hostility than one's sibling) and sibling differences in behavior problems was small but significant. Associations were stronger for differential hostility compared to differential warmth and for differential externalizing compared to differential internalizing behavior problems. Particularly marked was the finding that siblings who received more hostility from their parents showed higher levels of externalizing behavior problems. Future research investing in further dismantling the association between within-family PDT and sibling differences in adjustment is warranted to better understand why parents treat siblings differentially and to guide family support initiatives.