Sibling differences and parents' differential treatment of siblings: A multilevel meta-analysis.

The current study used meta-analysis to ask whether age differences, sex differences, and family size are linked to differences in parental treatment, as well as whether effect-sizes were moderated by the way parental differential treatment (PDT) was measured, who reported on the PDT, and the domain of PDT. Between August 2015 and November 2020, PsycINFO, Google Scholar, and PubMed Central were searched for articles relating to parental differential treatment; additionally, 13 sibling relationship scholars were contacted to collect unpublished analyses or unused data. Multilevel data came from 13,628 unique participants across 1,388 effect sizes nested within 66 sources (articles/raw data sets), nested within 23 unique samples (74% from North America; 26% from Western Europe). Multilevel meta-analysis conducted in R with the metafor package showed greater differences in parental treatment when siblings were further apart in age or a different sex. The main effects for age spacing, however, were moderated by several factors, particularly the domain of parenting. Specifically, age spacing was linked only to PDT based on control or autonomy granting, meaning when siblings were further apart in age, parents granted more autonomy to one sibling over another. Results were limited, however, by limited sample sizes at the sample level. Overall, findings suggest that parents may, in part, treat siblings differently because they are different to begin with. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Associations between older siblings' substance use and younger siblings' substance use intentions: Indirect effects via substance use expectations.

OBJECTIVE: We examined the direct and indirect effects of older siblings' substance use behaviors (i.e., cannabis and e-cigarettes) on younger siblings' later substance use intentions via their substance use expectations. MATERIAL AND METHODS: Data were collected from 682 families (N = 2,046) with two adolescent siblings (older siblings: M age = 15.67 years, 51% female; younger siblings: M age = 13.14 years, 48% female) and one parent (M age = 45.15 years; 85% female). Participants completed annual online surveys at two occasions. Older siblings reported on their cannabis and e-cigarette use frequencies (Time 1) and younger siblings reported on their substance use expectations (Time 1) and intentions (Time 1 and 2); parents reported on adolescents' sociodemographic characteristics and their own substance use (Time 2). RESULTS: Structural equation modeling results suggested that older siblings' cannabis and e-cigarette use was indirectly related to younger siblings' later intentions to use these substances through their positive expectations about substances, after accounting for younger siblings' earlier intentions to use substances and control variables including parents' and friends' use. There were no significant direct relations between older siblings' cannabis or e-cigarette use and younger siblings' intentions to use them. CONCLUSIONS: Findings indicate that older siblings are critical and unique socialization agents of younger siblings' expectations and intentions to use substances. Intervention and prevention programs that target adolescents' substance use should consider the ways in which siblings shape each other's substance use.