Abstract
Increasing evidence suggests that within-person variation in affect is a dimension distinct from mean levels along which individuals can be characterized. This study investigated affect variability's association with concurrent and longitudinal mental health and how mean affect levels moderate these associations. The mental health outcomes of depression, panic disorder, self-rated mental health, and mental health professional visits from the second and third waves of the Midlife in the United States Study were used for cross-sectional (n = 1,676) and longitudinal outcomes (n = 1,271), respectively. These participants took part in the National Study of Daily Experiences (NSDE II), where they self-reported their affect once a day for 8 days, and this was used to compute affect mean and variability. Greater positive affect variability cross-sectionally predicted a higher likelihood of depression, panic disorder, mental health professional use, and poorer self-rated mental health. Greater negative affect variability predicted higher panic disorder probability. Longitudinally, elevated positive and negative affect variability predicted higher depression likelihood and worse self-rated mental health over time, while greater positive affect variability also predicted increased panic disorder probability. Additionally, mean affect moderated associations between variability and health such that variability-mental health associations primarily took place when mean positive affect was high (for concurrent mental health professional use and longitudinal depression) and when mean negative affect was low (for concurrent depression, panic disorder, self-rated mental health, and longitudinal self-rated mental health). Taken together, affect variability may have implications for both short- and long-term health and mean levels should be considered. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s42761-024-00238-0.