Is Hostile Rumination a Amplifier or a Risk Marker? Daily Anger–Aggression Processes in Young Adults

Background: Hostile rumination (HR), the tendency to dwell on perceived offenses and retain hostile thoughts, has been linked to higher anger and aggressive behavior (Caprara, 1986; Caprara et al., 2007; Wilkowski & Robinson, 2010). Since anger and aggression can have substantial interpersonal costs in young adulthood, it remains unclear how HR may exacerbate the effect of anger on aggression during daily life. Purpose: This study addressed this gap by examining associations between HR and young adults’ daily anger and aggression. Methods: Italian young adults (N = 254; 18–33 years; 56.3% women) completed a 21-day daily diary of anger and aggressive behavior; baseline HR was assessed. Dynamic Structural Equation Modeling (DSEM) estimated between-person differences across days and within-person day-to-day dynamics, including whether HR moderated the across-day anger–aggression path. Results: Contrary to expectations, baseline HR predicted a higher level of anger at the between-person level (b = .080, p = .023), but was unrelated to within-person fluctuations in anger or aggression. It did not moderate the within-person anger–aggression association. At the within-person level, we only found a carry-over effect of aggression (b = .224, p = .021), indicating daily persistence. Conclusion: Findings indicated that HR is more closely tied to daily anger than to its day-to-day relation between anger and aggressive behavior. At the same time, HR acts as a risk factor that may indirectly heighten the risk for aggressive behavior in young adults, potentially via elevated anger. Moreover, the results align with prior work suggesting that aggressive behavior shows temporal persistence.