Positive affect inertia uniquely differentiates formerly depressed individuals from healthy controls: An ecological momentary assessment study

Previous studies have shown that emotional dynamics, that is, moment to moment variability and inertia of emotional states, are related to depression, but have no significant contribution after their overlap with mean affect is taken into account. However, few studies considered clinical samples. In our study, we compared a sample of euthymic formerly depressed persons (n = 94) at high risk of depression recurrence and healthy controls with no history of depression (n = 56), while using ecological momentary assessment data collected 10 times per day. The samples differed with respect to indicators of negative and positive affect dynamics computed from ecological momentary assessment data. However, when jointly considering all of emotional variability, inertia, and mean affect, only emotional inertia emerged as a significant predictor of group assignment. Specifically, the higher emotional inertia of positive affect proved to be the most influential predictor of belonging to the sample of formerly depressed persons versus being a healthy control. The finding remained even after controlling for differences in depressive symptoms between the samples. These findings indicate that positive affect inertia may characterize formerly depressed persons after symptoms have subsided, potentially indicating vulnerability for recurrence of depression episodes.