Social Media Use and the Quality of Family Relationships: A Six-Wave Longitudinal Study of Within-Family Effects from Age 10 to 20.

Adolescents and adults spend several hours a day on social media, raising concerns that extensive social media use may negatively affect family life. However, it remains unclear whether social media use is associated with changes in family relationship quality, as prior research has not separated stable between-family differences from within-family prospective effects and has often relied on single-informant data. These limitations risk inflating associations through shared methods variance and invite misinterpretation of cross-sectional links as developmental processes. Data were drawn from two birth cohorts from Trondheim, Norway, followed across six biennial waves from ages 10 to 20 (n = 979, 52.20% girls). Adolescents' frequency of checking social media, social media activity, and social media screen time were assessed using interviews and objective measures. Parents' frequency of checking social media and problematic social media use were assessed using questionnaires. Adolescents reported on their closeness and conflicts with their parents. Attachment was measured by self-report and observation of parent-child interaction, while family functioning was assessed by both adolescent- and parent-report. Using random intercept cross-lagged panel modelling, no evidence was found for either between-family associations or within-family prospective links between adolescents' and parents' social media use and poorer quality of family relationships, family functioning, or attachment. These findings suggest that normative variation in social media use is unlikely to be a meaningful driver of changes in family relationship quality, and that concerns about everyday social media use harming family life may not be warranted.