Waking up on the wrong side of the bed: sleep duration moderates the association between adolescent trait aggression and observed aggressive behaviour

Introduction Prior research suggests that insufficient sleep can increase aggressive behaviour in adolescents. However, few studies have employed controlled designs, but none have incorporated objective measures of aggression. Moreover, the potential moderating role of sleep in the relationship between trait aggression and aggressive behaviour remains unexplored. This study addressed these gaps by examining whether sleep duration and quality moderate the association between trait aggression and objectively measured aggressive behaviour in adolescents. We hypothesised that adolescents higher in trait aggression would be more sensitive to poor sleep. Method Thirty-four adolescent female participants spent one night in the Flinders University Sleep and Psychology Lab. Sleep duration was assessed using a consumer-grade sleep-tracking wearable, and sleep quality was self-reported. The following morning, participants underwent a noxious aggression provocation paradigm, after which behavioural aggression was assessed using a modified Hot Sauce Paradigm, measured via the weight of allocated wasabi paste. Trait aggression was measured using the Buss–Perry Aggression Questionnaire (BPAQ). Results Sleep duration significantly moderated the relationship between trait aggression and aggressive behaviour, with shorter sleep predicting greater aggression among participants higher in trait aggression ( R 2 change = 0.11, p = 0.03). No such moderating effect was observed for self-reported sleep quality. Discussion These findings suggest that adolescents high in trait aggression may be particularly susceptible to the behavioural consequences of shorter sleep. Ensuring adequate sleep could, therefore, be especially important for reducing aggression in this subgroup. This study extends prior research by demonstrating the moderating role of objectively measured sleep duration on aggression using a controlled design and a behavioural outcome measure, offering new insights for both theoretical models of aggression and the development of targeted, sleep-based interventions for at-risk youth.