Social outsiderhood - particularly loneliness and ostracism - has a significant impact on mental health issues such as internalizing symptoms (e.g., depression, anxiety) and externalizing symptoms (e.g., aggression, conduct problems). Yet, the mechanisms underlying these effects are multifaceted and likely include multiple mediating processes that may either amplify or mitigate the emergence of internalizing and externalizing symptoms. This cross-sectional study examines whether digital behaviors - social media use and gaming - mediate the relationship between school-based loneliness, school-based ostracism, and externalizing and internalizing symptoms in Finnish adolescents. Data were collected from 1,742 secondary school students (mean age 14.9 years; 47.6% male). Results reveal that both social media use and gaming were only weakly correlated with school-based loneliness, school-based ostracism, and mental health outcomes. Mediation analyses demonstrated that neither social media nor gaming robustly mediated the link between social disconnection and externalizing and internalizing symptoms. However, social media use weakly but significantly mediated the ostracism - internalizing symptoms link among girls, and gaming partially mediated the loneliness - internalizing symptoms link among boys. The findings suggest that digital behaviors are not primary explanations for the impact of school-based loneliness and ostracism on adolescent mental health. Future research should utilize longitudinal approaches and other measures of digital engagement to further clarify these relationships and identify alternative mediating processes.