Are “night owls” or “morning larks” more likely to delay sleep due to problematic smartphone use? a cross-lagged study among undergraduates

Sleep is an important physiological process, but staying up late has become a worldwide problem, particularly among university students. Sleep procrastination has been found to associated with sleep biorhythms and problematic smartphone use ("PSU") in previous studies. This two-wave study examines the longitudinal reciprocal relationship between PSU and sleep procrastination, together with the moderating role of sleep biorhythms. Participants comprised 1,423 Chinese university students. The results revealed that PSU and sleep procrastination are reciprocally related. Additionally, sleep biorhythms moderated this relationship, as PSU at T1 significantly predicted sleep procrastination at T2 for the morning larks group but not the night owls group. Accordingly, both PSU and sleep biorhythms should be considered when developing interventions for sleep procrastination.