Slow-wave sleep (SWS) is essential for physical recovery and emotional regulation (Shapiro et al., 1981; Santos et al., 2021). Additionally, SWS has been posited to be reduced in those with major depressive disorder (MDD) (Benca et al., 1992). Some externalizing traits of depression include aggression and irritability, which overlap with psychopathic traits, which have also been linked to altered sleep patterns (Rahafar et al., 2022; Genunchi, M., 2015). This study focused on exploring these traits and their relationship to SWS in individuals with MDD. Given that sex differences often play a role in both depression and psychopathy, this study also investigated differences between males and females (Plante et al., 2012; Sanz-García et al., 2021).