The feedback whirlpool of early childhood sleep and behavior problems.

It is a classic chicken or egg conundrum: across the many crosssectional studies in the literature reporting significant associations between childhood sleep problems and emotional/ behavioral problems, some consider sleep the exposure and behavior the outcome in their statistics and tables1,2 and some examine behavior problems as the predictor and sleep problems as the outcome.3 Although a cross-sectional study cannot demonstrate the causal sequence, many parents point out that it sometimes seems to flow in both directions, setting up a feedback whirlpool of despair. Inadequate sleep seems to beget tired meltdowns, which in turn delay sleep onset, potentially setting the child up for even more behavior problems the next day. Longitudinal research to date supports this idea that the effects are bidirectional.4 A variety of potential mediators are plausible, ranging from neuroendocrine pathways5 to the effect early childhood sleep problems have on parents’ sleep and mood.6 From a scientific perspective, this is what makes the epidemiology of child sleep and behavior both challenging and intriguing. But from a clinical and public health perspective, the possible bidirectional nature of the relationship has critical implications for intervention. Although intervening on sleep may have the bonus effect of reducing child behavior and emotional problems,7,8 it is possible that long-term success might require either starting early (before that feedback loop is set in play) or acting on sleep, behavior, and emotional problems in conjunction. In this issue of JAMA Pediatrics, Sivertsen et al9 used a large birth cohort to assess the longitudinal impact of early childhood sleep on emotional and behavior problems. Their research presents an important contribution to the literature for 2 reasons. First, they showed that early childhood sleep problems are not only associated with greater risk for later emotional and behavior problems but that this holds true even when adjusting for baseline levels of emotional and behavior problems. Although all groups showed the expected decrease in CBCL (Child Behavior Checklist) internalizing and externalizing scores from 18 months to 5 years that happens as young children mature and gain self-regulation skills, those children with sleep problems at 18 months experienced significantly fewer expected behavioral and emotional gains compared with their peers. Other studies looking at this longitudinal relationship in young children have sometimes failed to take this into account, leaving the reader to wonder whether sleep problems during infancy and toddlerhood lead to later behavioral problems or whether the findings merely reflect a persistence in behavior problems that were already more likely to be present in children with sleep problems at baseline.10 Second, Sivertsen et al9 demonstrated these effects in a younger age group than has generally been studied. In regards to the mixed conclusions regarding the long-term effect of infant sleep problems during the first year of life,11,12 this study informs our understanding of where this feedback loop might start to spin. Add to this the awareness that behavioral sleep intervention may be easier and more effective during the toddler years in contrast to later childhood13 and the current findings increase the stakes on early intervention for childhood sleep problems in the clinical setting. These findings also strengthen the hypothesis that childhood sleep problems may play a mediating role in many social determinants of health. Poverty, conflict in the home, living in an unsafe environment, and other adverse childhood experiences are all significant risk factors for child sleep problems14 that may affect how the child’s neuroendocrine system responds to the stresses in their environment and impair executive function and emotional regulation, leading to increased risks for a wide range of adverse health and social consequences. The need to improve early childhood sleep is not only a family issue or a clinical problem but may be critical from a public health perspective as well.