The popularity of social media use among adolescents has raised concerns about the potentially harmful effects of social media use on adolescents' sleep. Since longitudinal research considering this relationship is scarce, the present two-wave longitudinal study of 2021 secondary school students (Mage = 13.86, SD = 1.25) examined whether frequency of social media use and problematic social media use predicted adolescents' bedtime and quality of sleep. Moreover, the protective role of parental rules regarding Internet and smartphone use one hour before sleep was examined. The findings indicated that strict parental rules about Internet and smartphone use before sleep might prevent negative consequences of social media use on bedtime and sleep quality, but only among less engaged social media users. Once adolescents are highly engaged social media users, strict parental rules do not seem to prevent negative media influences on sleep. This implies that limiting Internet accessibility before bedtime can help prevent adolescents' sleep problems, but that regulation is less effective for adolescents who are already highly involved in social media use.
Keywords: adolescents; parental rules; parenting; sleep; social media addiction; social media use.