Daily Anger and Aggression in Young Adults: The Moderating Role of Loneliness

Background: Aggression is a public health concern, particularly in young adulthood, when rates of aggressive behavior tend to peak (Archer, 2004). Loneliness, a form of social pain, increases vulnerability to anger, which motivates aggressive behavior (DeWall et al., 2010; Wilkowski & Robinson, 2010). However, how these constructs interact in daily life remains poorly explored, as most existing evidence is based on cross-sectional designs that cannot capture within-person dynamics. Purpose: This study examined how anger and loneliness predict aggressive behavior in 21-day daily diary in a sample of 76 Italian young adults. Methods: Using multilevel modeling (MLM), we examined daily effects of anger and loneliness on aggression, as well as the interaction between anger and loneliness, controlling for gender. Results: At the within-person level, feeling angrier than usual predicted higher aggression (b = .216, p < .001). At the between-person level, those who reported more anger also reported more aggression (b = .497, p < .001). The between-level loneliness and anger interaction was significant (b = .176, p = .004). Simple-slope analyses indicated that anger was strongly associated with aggression among participants higher in trait loneliness (+1 SD; b = .65, p < .001) than among those lower in loneliness (-1 SD; b = .26, p < .001).  Conclusion: Findings indicate that daily aggression is associated not only with day-to-day elevations in anger but also with between-person differences; at the between-person level, loneliness strengthens the anger–aggression association. Interventions targeting anger regulation and loneliness-prone individuals may help reduce aggression in young adulthood.