Beyond main effects? Affect level as a moderator in the relation between affect dynamics and depressive symptoms

There are opposing views on the relative adaptiveness of affective change and its role in depression. Some studies link depression to more changes in affect (i.e., higher variability), others to a greater resistance to change (i.e., higher inertia). Our study provides an explanation for such inconsistencies by hypothesizing that the relation between affect dynamics and depression differs as a function of mean levels of affect. We analyzed data from seven studies that measured affect in daily life in adolescents and young adults (N = 1,448, age range = 11.7-29.9 years, 64.8% females). We tested main and interaction effects of affect dynamics (variability and inertia) and affect level on depressive symptoms, separately for positive affect (PA) and negative affect (NA). For PA, we found mostly main, but no interaction effects. Depressive symptoms were associated with more PA variability and less PA inertia, indicating that depressive symptoms in young people may be characterized by more fluctuating PA, independent of PA mean levels. For NA, we found a significant moderation effect between NA variability and NA levels for depressive symptoms at baseline. For individuals with low NA levels, high NA variability was associated with more depressive symptoms. In contrast, for individuals with high NA levels, high NA variability was associated with fewer depressive symptoms. These results suggest that the relative adaptiveness of NA variability depends on overall NA levels and underscores the need for a more nuanced understanding of affect variability in depression.