Exploring the Dark Tetrad and sleep variables: The role of sadism within the model.

The Dark Tetrad traits are increasingly studied constructs but remain relatively underexplored in relation to sleep health, particularly regarding everyday sadism. The present study examined whether Machiavellianism, narcissism, psychopathy, and sadism uniquely predict multiple dimensions of sleep health. Self-report data were collected from an online sample (N = 422) assessing Dark Tetrad traits alongside sleep outcomes measured using the Pittsburgh Sleep Quality Index and the Sleep Hygiene Index. Hierarchical regression analyses revealed psychopathy to be the most consistent positive predictor of poorer sleep outcomes, including sleep disturbances, daytime dysfunction, and global sleep dysfunction. In contrast, narcissism showed several negative associations with sleep outcomes once shared variance with other dark traits was controlled, suggesting a suppression effect. Machiavellianism showed no reliable unique associations with sleep variables, whereas sadism demonstrated a small association with global sleep dysfunction but was not reliably associated with specific sleep components. Overall, the findings suggest that Dark Tetrad traits may relate to sleep health through partially distinct behavioural pathways, with the clearest associations emerging for subjective sleep experiences captured by the PSQI rather than core physiological sleep parameters.