Interrelations between daily stress processes and Big Five personality trait changes over 20 years.

Personality is characterized by continuity and the capacity to change across the lifespan. Integrative personality frameworks imply that variability in daily life experiences has the potential to evoke longer term changes in personality over time. However, strong tests of this assumption across the adult lifespan are relatively rare. We examined the interrelations between changes in daily stress reactivity and changes in Big Five personality traits over a nearly 20-year period. Three measurement bursts from the National Study of Daily Experiences ( = 2,022; 55% female) each included daily measures of stressor exposure and negative affect across eight consecutive days (yielding 33,942 days of data across 18 years of adulthood). At each wave, participants reported on their personality traits (i.e., openness, conscientiousness, extraversion, agreeableness, neuroticism). Multilevel structural equation modeling simultaneously modeled stress reactivity at Level 1; longitudinal changes in stress reactivity at Level 2; and the interrelations between changes in stress reactivity and changes in personality traits at Level 3. Higher reactivity at baseline was associated with lower levels of extraversion and conscientiousness and higher levels of neuroticism at baseline. Further, increases in reactivity across the 18-year period were associated with declines in extraversion, agreeableness, and openness. Changes in reactivity were not related to changes in neuroticism or conscientiousness. These findings clarify how changes in daily experiences are related to broader personality changes and inform integrative frameworks of personality development across the adult lifespan. (PsycInfo Database Record (c) 2025 APA, all rights reserved).