Genetic and environmental influences on parenting, sibling conflict, and childhood sleep in five-year-old twins
Understanding how interpersonal relationships, such as parenting and sibling relationships, may contribute to early sleep development is important, as early sleep dysregulation has been shown to impact later sleep behavior (Sadeh & Anders, 1993), as well as cognitive and behavioral functioning (Gregory et al., 2006; Soffer-Dudek et al., 2011). In addition, twin studies provide an optimal opportunity to estimate genetic and environmental contributions to parenting, sibling relationships and child sleep, as they are influenced by both genetic and contextual factors. As such, the current thesis examined whether parental punitive discipline and sibling conflict were associated with child sleep duration, dysregulation and daytime sleepiness at 12 months, 30 months, and five years in a longitudinal sample of young twins recruited through birth records (Lemery-Chalfant et al., 2013). Mixed model regression analyses and quantitative behavioral genetic models (univariate and bivariate) were conducted to explore bidirectional relations and estimate genetic and environmental contributions to parental punitive punishment, sibling conflict and child sleep parameters. Sleep duration and dysregulation showed stability over time. Parental punitive discipline did not predict concurrent or future sleep parameters, nor were there bidirectional relations between punitive discipline and child sleep behaviors. Greater sibling conflict at five years was associated with shorter concurrent child sleep duration and greater daytime sleepiness, suggesting that sibling conflict may be a critical interpersonal stressor that negatively impacts child sleep. Shared environmental factors also accounted for the greatest proportion of the covariance between sibling conflict and sleep duration and daytime sleepiness at five years. These findings hold promise for sleep and sibling interaction interventions, including educating parents about fostering positive sibling relations and teaching caregivers to utilize specific parenting behaviors that may encourage better child sleep behaviors (e.g., establishing bedtime routines). Future studies should aim to understand the nuances of associations between family relationships (like punitive discipline and sibling conflict) and child sleep, as well as other explore person- and family-level factors, such as child negative emotions and parenting, that may influence associations between family relationships and child sleep.