It has been speculated that defending victims of bullying is stressful for youth, and may contribute to poor mental health
among those who regularly intervene to defend their victimized peers. However, the extant literature is thus far primarily
limited to correlational, single-informant studies. The current study examined the concurrent and prospective mental health
costs (e.g., social anxiety, depressive symptoms) of peer-reported defending among 4085 youth (43.9% boys; Mage=14.56,
SD =0.75). Moreover, we examined two potential moderators (victimization and popularity) of the association between
defending and internalizing problems. Analyses revealed that there was no evidence of a direct, positive relationship between
defending and internalizing symptoms. However, a positive, concurrent association was found between defending and social
anxiety, but only among youth who reported that they were also victims – the association was negative among non-victimized
youth. In addition, both peer-reported victimization and social status were found to moderate the longitudinal relationship
between defending and later symptoms of depression. Specifcally, among low-status highly victimized youth, defending was
associated with an increased risk of experiencing symptoms of depression, whereas high-status youth who were rarely seen
as victims reported decreased symptoms of depression at T2 if they also had a reputation for defending others. The fndings
suggest that defending others is likely not a risk factor for youth who are not already vulnerable and/or have the protection
of high status, and may actually have a protective efect for these youth.