Children's sleep and adjustment: a residualized change analysis.

Child sleep problems (Meltzer & Mindell, 2006) are highly prevalent and are associated with adjustment problems (El-Sheikh, Kelly, Buckhalt, & Hinnant, 2010). Research is clarifying relations between sleep and adjustment yet several important gaps remain. Longitudinal studies with more than two waves are scarce, not much is known about sleep trajectories of school-age children or their sequelae and studies of the impact of persistent sleep problems are scant (Jansen et al., 2011). Using data collected over three years, we examined whether initial levels and rates of change in children’s sleep problems predicted T3 adjustment. We also assessed the moderating role of child sex, ethnicity, and family socioeconomic status (SES) in these links. We examined sleep problems along a continuum in typically developing children, which were indicated by increased sleepiness and sleep/wake problems (S/WP) (i.e., insufficient sleep and difficulty initiating and maintaining sleep). We examined the effects of these sleep measures on children’s cognitive functioning in Bub, El-Sheikh, & Buckhalt (2011) using the same sample. Child sleep problems including duration, quality, and daytime sleepiness are associated with symptoms of depression and anxiety (Chorney, Detweiler, Morris, & Kuhn, 2008) as well as anger and aggression (Chervin, Dillon, Archbold, & Ruzicka, 2003). Across two waves of data, parent-reported child sleep problems at age four years predicted an increase in depression, anxiety and aggression during mid-adolescence (Gregory & O’Connor, 2002). With an independent sample from that utilized in the present study, more S/WP were associated with increases in internalizing and externalizing symptoms two years later (El-Sheikh et al. 2010). Sleep problems can disrupt processes mediated in the prefrontal cortex (PFC), including executive functioning needed for emotion regulation (Jones & Harrison, 2000), which in turn put children at risk for both internalizing and externalizing problems (Dahl, 1996). Researchers have begun to use individual or latent growth modeling to examine cross-domain associations but work in this area is relatively nascent. Adolescents who experienced a faster decline in sleep duration over time were more likely to exhibit increases in depression symptoms over three years (Fredriksen, Rhodes, Reddy & Way, 2004). Further, children whose sleep problems (mother report) increased at a faster rate also exhibited increasing externalizing behaviors (teacher report) (Goodnight, Bates, Staples, Pettit, & Dodge, 2007). The prevalence of children’s sleep problems may be higher among African (AAs) than European Americans (EAs), and among those from lower SES backgrounds (Buckhalt, El-Sheikh, Keller & Kelly, 2009). Examination of sociocultural moderators of the link between children’s sleep and their adjustment is critical for identifying for whom and under which conditions sleep has a protective or vulnerability function. Consistent with views of cumulative risk (e.g., Buckhalt, 2011), ethnic minority or economically disadvantaged children may be especially vulnerable to the negative effects of sleep problems and emerging evidence supports this proposition for children’s adjustment (El-Sheikh et al., 2010). Findings pertaining to sex differences in children’s sleep are inconsistent and little work has examined child sex as a moderator of the sleep-adjustment connection. Girls may have better sleep quality (Buckhalt et al., 2009) or longer duration (Fredriksen et al., 2004); opposite findings have been reported (Gaina et al., 2007). In their 3-wave study with adolescents, Meijer, Reitz, Dekovic, van den Wittenboer, and Stoel (2010) found that sleep problems predicted increased adjustment problems more robustly for boys. Further, because girls compared to boys are more susceptible to internalizing symptoms in adolescence (Hankin & Abramson, 2001; Van Oort et al., 2009), we investigated child sex as a moderator of the sleep-adjustment link. This study builds on the literature in important ways. We examined several outcomes including depression symptoms, anxiety, and anger/aggression (referred to as anger for brevity). Building on the scarce longitudinal literature most of which is with two study waves, research questions were examined using three waves of data, a requirement for linear growth modeling, thereby allowing for a more thorough explication of associations. With an independent sample, we found that S/WP predicted increases in internalizing and externalizing symptoms two years later (El-Sheikh et al., 2010). The present investigation utilizes three waves of data and examines not only initial S/WP but also changes in sleep as predictors of adjustment. We expected that children with more sleep problems at T1 and increases in sleep problems over time would have poorer adjustment at T3 and expected more pronounced relations for AA children, those from lower SES homes, and girls (similar to findings reported by Bub et al., 2011 in relation to cognitive outcomes).