A longitudinal daily diary study of stress, self-esteem fluctuation, and mood variability in adolescents.

Adolescence represents a developmental phase marked by profound and rapidly shifting emotional states. While some adolescents exhibit pronounced, day-to-day mood variability, others remain comparatively stable. Although emotional fluctuation has long been considered a core feature with implications for health and well-being, the determinants underlying these substantial individual differences remain insufficiently understood. To address this, we conducted a longitudinal study using daily app-based assessments, aiming to explore whether perceived stress and self-esteem dynamics help explain why some adolescents show greater mood variability than others. We asked N = 70 adolescents to rate their self-esteem, positive, and negative mood once per day for 15 days. For data analyses, we used path analytic mediation modeling. Fluctuation of self-esteem (FSE) significantly predicted both fluctuation of positive mood (FPM; b = 0.282, 95% CI [0.101, 0.464], p = .0.002) and fluctuation of negative mood (FNM; b = 0.395, 95% CI [0.147, 0.644], p = 0.002) indicating that greater variability in self-esteem is associated with greater mood fluctuation. Moreover, perceived stress (PS) significantly predicted FSE (b = 0.057, 95% CI [0.012, 0.102], p = 0.013), suggesting that higher perceived stress was associated with greater self-esteem fluctuation. Significant indirect effect emerged for PS on FPM (b = 0.016, 95% CI [0.003, 0.030], p = 0.019) and on FNM (b = 0.023, 95% CI [0.002, 0.043], p = 0 .028) via FSE, confirming a mediating role of self-esteem fluctuations. This study showed that perceived stress was associated with fluctuations in self-esteem, which were related to mood variability among adolescents. These findings suggest that stress reduction could be explored as a potential avenue for future interventions.