Within-person associations between sleep duration and next-day suicide risk: evidence from EMA and actigraphy

Introduction: Despite suicide being the second leading cause of death among young adults worldwide, predicting suicide risk remains challenging, as the ability to monitor short-term fluctuations in suicidal vulnerability in real time is still limited. Accordingly, recent research has shifted toward the identification of proximal risk factors, namely dynamic processes that may signal short-term increases in suicide risk. The present study examined whether daily variations in sleep, also in interaction with positive and negative life events, predict short-term changes in suicide risk in a sample of university students. Methods: A total of 104 university students were enrolled (mean age = 22.3 ± 2.0 years; 72.1% females). For a week, smartphone-based ecological momentary assessment was used to measure suicide risk, positive and negative affect, and positive and negative daily events, with participants completing four surveys per day. During the same period, sleep was continuously monitored using wrist-worn actigraphy. Mixed-effects linear models were conducted to examine within- and between-person associations between total sleep time, and next-day suicide risk, as well as their interactions with daily positive and negative life events. The study protocol was preregistered on OSF (https://osf.io/zrmf7). Results: At the within-person level, shorter-than-usual total sleep time predicted a subsequent increase in next-day suicide risk. Positive and negative daily events did not moderate this association. Conclusions: Taken together, these findings suggest that suicide risk in university students is linked to day-to-day changes in sleep. The integration of wearable devices, such as wrist-worn actigraphy, with EMA offers a promising approach for capturing real-time changes in suicide risk among university students, thereby facilitating the development of time-sensitive prevention strategies.