Between Support and Risk: The Dual Role of Peer Relationships in Adolescents’ Mental Health

Background/Objectives: Adolescence is a developmental stage marked by profound transformations and heightened vulnerability to mental health difficulties, with peer relationships playing a central role, as they provide both protective and risk factors for adolescents’ mental health and well-being. This study aims to characterize Portuguese adolescents’ perceptions of how peers and friends influence their mental health, both positively and negatively. Methods: Participants were 99 adolescents aged 14–19 years old enrolled in a Portuguese secondary school. Data were collected through two open-ended questions and participants responses were analyzed using a mixed-methods approach, qualitative and quantitative. Results: Bullying and aggression were the most frequently reported negative influences, followed by peer pressure for inadequate behavior, toxic or false friendships, lack of support, criticism, and social exclusion. Conversely, social support was the most cited positive influence, alongside connection and belonging, promotion of emotional well-being, positive peer characteristics, and social learning. Conclusions: Findings support the dual role of peer relationships, which may either exacerbate vulnerability or strengthen resilience. The study underscores the importance of school-based prevention strategies that reduce bullying and peer aggression while fostering prosocial climates and supportive peer interactions.