The power of friendships in adolescents' daily lives: Bi-directional within-person associations between friendship interaction quality and affect.

Friends play a critical role in adolescent development, yet relatively little is known about how friendship interactions in adolescents' daily lives relate to their affective experiences. This study examined bidirectional associations between friendship interaction quality (i.e., warmth and conflict) and momentary affect, as well as whether these associations were moderated by individual differences (i.e., depressive symptoms, habitual rumination, and gender). 247 adolescents (Mage = 12.94, SDage = 0.41, 108 females, 224 identified as Belgian) participated in an ecological momentary assessment (EMA) study involving five surveys per day over two consecutive weeks. Pre-registered Dynamic Structural Equation Modeling (DSEM) analyses revealed that higher momentary negative affect was associated with greater friendship conflict in the subsequent hours, whereas friendship warmth was associated with higher subsequent positive affect. These associations were not consistently moderated by depressive symptoms, habitual rumination, and gender. Exploratory analyses examining temporarily closer associations (i.e., affect and friendship interaction quality assessed at the same time) suggest that conflictual interactions with friends were associated with higher levels of negative affect and lower levels of positive affect, whereas, warm interactions with friends were associated with lower levels of negative affect and higher levels of positive affect. Overall, findings highlight short-term, micro-level associations between adolescents' friendship interaction quality and their affective experiences in daily life.