PURPOSE: A social gradient in adolescent mental health exists: adolescents with higher socioeconomic status (SES) have fewer mental health problems than their peers with lower SES. Little is known about whether adolescents' societal beliefs play a role in this social gradient. Belief in a just world (BJW) may be a mediator or moderator of the social gradient in adolescent mental health. METHODS: Using data from 848 adolescents (Mage = 17) in the Netherlands, path analyses examined whether two indicators of BJW (general and personal) mediated or moderated the associations between two indicators of SES (family affluence and perceived family wealth), and four indicators of adolescent mental health problems (emotional symptoms, conduct problems, hyperactivity, and peer problems). RESULTS: Adolescents with lower family affluence and lower perceived family wealth reported more emotional symptoms, and the association between perceived family wealth and emotional symptoms was mediated by lower personal and general BJW. Furthermore, higher personal BJW amplified the negative association between SES and peer problems. CONCLUSION: This study suggests BJW may both mediate and amplify the social gradient in adolescent mental health. Adolescents' beliefs about society may be important to include in research aimed at understanding this social gradient
