Stability and Change in Wellbeing Throughout Adolescence and Its Relationship with Life Events: A Longitudinal Twin Study.

Wellbeing-the balance of positive and negative affect and life satisfaction-is closely tied to mental health. However, the sources of stability and change and how life events shape wellbeing are not well understood. Data from the Oslo University Adolescent and Young Adult Project (2,879 individuals from 1,483 families) provided wellbeing and life‑event data across three waves ~ 2 years apart (ages 12-18 at Wave 1). We used a trivariate Cholesky decomposition to estimate genetic and environmental contributions to wellbeing, and genetically informative random intercept cross‑lagged panel models (RI‑CLPMs) to test prospective effects of life events on wellbeing. Wellbeing showed moderate stability, predominantly driven by genetic influences (81%). Cross-sectional heritability was about 50% at Waves 1-2 and declined to 26% at Wave 3. Negative life events were correlated with lower wellbeing (concurrent r = - 0.34 to - 0.28; 2-year r = - 0.26 to - 0.19; 4-year r = - 0.22 to - 0.12). However, RI‑CLPMs indicated minimal longitudinal effects of life events on wellbeing after accounting for genetics and trait stability: negative dependent life events explained 1% of change from Wave 1 to Wave 2 and ≈ 0% (non-significant) from Wave 2 to Wave 3. Genetic factors primarily account for stability in wellbeing, while measured life events showed limited prospective influence on wellbeing levels. Future research should combine richer genetically informed longitudinal designs (e.g., measured genotypes and GxE models) and examine biological pathways and person-level processes (e.g., neural and epigenetic mechanisms) to clarify pathways influencing wellbeing and inform interventions.