Sleep is essential for children’s and adolescents’ physiological, cognitive, and emotional development. However, sleep issues — including sleep deficiency, rhythm disturbance, and sleep irregularity — have become increasingly prevalent public health concerns. Although existing research has demonstrated the detrimental impact of sleep issues on internalizing problems among children and adolescents, several gaps remain in the literature. Specifically, most studies examining the relationship between sleep duration and internalizing problems have focused on linear associations, providing limited insight into non-linear relationships or optimal sleep duration thresholds among children and adolescents. Moreover, findings regarding the effects of sleep rhythm and sleep regularity on internalizing problems have been inconsistent. Furthermore, drawing on the differential susceptibility theory, which posits that individuals vary in their sensitivity to environmental experiences based on personal characteristics, it remained unknown whether these association are influenced by factors such as grade level and negative emotionality. To address these gaps, this study employed daily diary investigation to examine the associations between sleep duration, sleep rhythm (measured as sleep midpoints) and sleep regularity (measured as weekend catch-up sleep) and internalizing problems among children and adolescents, and whether these associations were moderated by grade level and negative emotionality.
Participants comprised 3, 197 primary and middle school students from Grade 4 to 9 (mean age 12.33 ± 1.72 years, 49.0% girls). Each participant first completed a daily sleep diary for seven consecutive days to report their sleep-wake patterns, including bedtime and wake time. Nocturnal sleep duration was calculated as the total hours between sleep-onset and wake-up time, and the sleep midpoint was defined as the halfway point between these two times. Weekend catch-up sleep was computed as the difference between weekday and weekend sleep duration. Following the diary investigation, participants self-reported their internalizing problems using the Youth Self-Report (YSR) and negative emotionality using the Early Adolescent Temperament Questionnaire-Revised (EATQ-R). Parents completed a brief survey to provide demographics information. Hierarchical regression analysis was conducted to examine effects of nocturnal sleep duration, sleep midpoint and weekend catch-up sleep on internalizing problems, as well as the moderating roles of grade and negative emotionality.
The present study revealed three key findings after controlling for demographics information. First, a U-shaped relationship was observed between nocturnal sleep duration and internalizing problems among primary school students with high levels of negative emotionality and among middle school students. The optimal sleep duration threshold is 10.39 hours for primary school students with highly negative emotionality and 9.09 hours for middle school students. Second, a later midpoint of sleep was significantly associated with greater internalizing problems among middle school students with high levels of negative emotionality. Third, a U-shaped relationship was also found between weekend catch-up sleep and internalizing problems among middle school students with low levels of negative emotionality, with the optimal threshold of weekend catch-up sleep is 1.10 hours. In contrast, a positive linear relationship was observed for middle school students with high levels of negative emotionality, indicating that longer weekend catch-up sleep was associated with greater internalizing problems.
In summary, the present study highlights the psychological risks associated with suboptimal sleep duration, delayed sleep midpoint, and extended weekend catch-up sleep, particularly in relation to internalizing problems among children and adolescents. These findings not only provide further empirical support for differential susceptibility theory, but also offer practical guidance for developing evidence-based sleep schedules to reduce the detrimental impact of sleep disturbances on the mental health of children and adolescents.
