Measuring Stability Across Multiple Domains of Mood and Affect

Authors

• Y Xiao
• J Johns
• KR Merikangas
• V Zipunnikov

Abstract

Introduction: Ecological Momentary Assessment (EMA) is an efficient tool for the daily assessment of subjective mood and sleep quality within large samples. We develop a novel statistical framework for capturing subject specific stability in several domains of mood and use this framework to compare subgroups diagnosed with mood disorders. Methods: 417 participants with mood disorder subtypes (Bipolar I [BPI], Bipolar II [BPII], Major Depressive Disorder [MDD] and controls) from a local community sample were assessed over 14 consecutive days with EMA. Information regarding six domains of mood (sad/happy, anxious/relaxed, tired/energetic, active/inactive, attention, and irritability) was self-reported 4 times per day on a Likert scale of 1-7. We normalize the responses at the subject level and then dichotomize the z-scores into a binary index representing values inside and outside of the subject-specific standard range. To measure cross-domain stability, or fluctuation in and out of the standard range within and between domains, we define and calculate the multivariate mean of squared successive differences (MMSSD) for scores across K domains, represented by a KxK matrix for each subject and regress the norms of these subject-specific matrices across groups. Results: We showed that while BPI (p=0.015*), BPII (p=0.008**), and MDD (p=0.042*) subjects spent more time outside their standard range of mood compared to controls, BPI (p=0.001**), and BPII (p=0.009**) but not MDD (p=0.115) , subjects showed greater instability in mood. Conclusion: In this work, we have proposed a novel composite index that characterizes the cross-domain stability among mood domains and demonstrated its ability to discriminate between mood disorder groups.

Scientific Focus Area: Epidemiology

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