Sleep deprivation has become a widespread phenomenon in contemporary society, especially among individuals with high job demands, those engaged in shift work, or those experiencing prolonged wakefulness. In modern occupational and social settings, insufficient sleep is no longer an occasional inconvenience but a chronic condition that affects a large proportion of the population. A growing body of research has shown that sleep loss impairs attention, working memory, executive control, emotional regulation, and decision-making, thereby increasing the likelihood of maladaptive judgments and behaviors. Its consequences therefore extend beyond general cognitive functioning and increasingly affect social cognition and morally relevant decision-making. Previous studies have primarily examined the effects of sleep deprivation on either unethical behavior or utilitarian choice in isolation. However, a systematic comparison of their differential mechanisms and underlying neural bases remains lacking.

This article adopts a narrative review design. Drawing on empirical studies in sleep research, moral psychology, and cognitive neuroscience, the reviewed literature was organized around two classes of morally relevant outcomes: unethical behavior in norm-violation contexts and utilitarian choice in sacrificial moral dilemmas. Representative paradigms, behavioral findings, and neural evidence were compared across these two domains. This review integrates the evidence from the perspective of key psychological processes, including cognitive control, self-regulatory resources, negative affect, harm aversion, and emotion-cognition integration, in order to identify both shared and distinct pathways through which sleep deprivation may influence moral decision-making.

Against this background, the present review examines the effects of sleep deprivation on two types of morally relevant outcomes, namely unethical behavior and utilitarian choice, and summarizes their underlying psychological and neural mechanisms, to provide a clearer theoretical account of the complex relationship between sleep deprivation and moral decision-making. Although these two outcomes differ conceptually, both involve the weighing of behavioral consequences, social norms, and value conflicts in complex social situations, and can therefore be regarded as important components of moral decision-making in a broad sense. Research on unethical behavior mainly focuses on forms of misconduct such as deception, cheating, and theft, and typically employs experimental paradigms such as the coin-flip task, the dice-roll task, and paradigms involving electric shocks. By contrast, research on utilitarian choice usually adopts moral dilemma paradigms, such as the trolley problem and its variants, including footbridge-type and everyday-life dilemmas, to examine how individuals make decisions in situations involving harming a few to maximize benefits for the many.

Existing studies suggest that sleep deprivation increases both unethical behavior and utilitarian choice; however the mechanisms underlying these effects may differ. Sleep deprivation appears to increase unethical behavior mainly by weakening cognitive control and increasing negative emotions such as hostility, thereby making individuals more vulnerable to immediate temptations and more likely to deviate from social norms. In contrast, in sacrificial moral dilemmas, the effects of sleep deprivation seem to be more closely related to changes in harm aversion, outcome evaluation, and the integration of emotional and cognitive processes. Although both types of outcomes may be influenced by reduced cognitive control, unethical behavior more directly reflects a failure to maintain normative constraints, whereas changes in utilitarian choice more strongly reflect altered ways of processing and integrating information in complex value conflicts. In addition, sleep deprivation does not affect unethical behavior and utilitarian choice in a simple or uniform manner; instead, both are jointly shaped by individual traits and social-contextual factors. However, the specific moderators differ between the two outcomes. The former is more often moderated by factors such as sex, moral disengagement, social consensus, social influence, caffeine intake, and task format, whereas the latter is more strongly shaped by emotional state, emotional intelligence, and situational attributes such as personal versus impersonal dilemmas. Therefore, the effects of sleep deprivation on unethical behavior and utilitarian choice appear to involve partially distinct mechanisms.

Future studies should develop or adopt a more unified framework to simultaneously estimate sleep-related parameters (e.g., sleep duration and sleep efficiency), and moral decision-making parameters (e.g., reaction time and decision threshold). This would help clarify how sleep deprivation alters specific computational processes underlying moral decision-making. In addition, combining polysomnography with neuroimaging techniques such as functional magnetic resonance imaging may help reveal whether sleep deprivation affects moral decision-making by weakening cognitive control functions associated with the dlPFC, disrupting value integration associated with the vmPFC, and enhancing emotional responses in limbic regions such as the amygdala. Future research should also adopt more systematic and standardized moral decision-making paradigms and integrate behavioral and neural indicators to better examine the restorative effects of sleep interventions and their underlying mechanisms.