2 - (SYM 28) Depressive Symptoms as a Heterogeneous and Constantly Evolving Dynamical System: Idiographic Depressive Symptom Networks of Rapid Symptom Changes Among Persons with Major Depressive Disorder

Major depressive episodes are conceptualized as a series of individual symptoms occurring most of the day for at least two weeks. Despite this operationalization, symptoms are highly variable among those meeting criteria for major depressive disorder (MDD), showing greater variation within and across days. Moreover, MDD is highly heterogeneous, varying considerably across people in both function and form. Recent efforts have examined MDD heterogeneity by investigating how symptoms influence one another over time across individuals in a system; however, these efforts have made the strong assumption that symptom dynamics are static and do not dynamically change over time. Nevertheless, it is possible that individual MDD system dynamics change continuously across time. As a part of the Tracking Depression Study, funded by the National Institute of Mental Health and the National Institute of General Medical Sciences, we sought to investigate how MDD symptom dynamics vary both across and within persons over time.

In the current study, individuals who met criteria for current MDD (N = 105; 86% women, 10% men, 2% non-binary, and 2% other; 82% White, 5% Asian, 8% Black, 2% American Indian or Alaskan Native, and 3% other; 92% non-Hispanic and 8% Hispanic) completed ecological momentary assessments of MDD symptoms three times a day for 90 days. We conducted time-varying vector autoregressive models to investigate the idiographic symptom networks across the entire sample. We then illustrated this finding with a case series of five persons with MDD (n = 5, 80% women, 20% men, 80% White, 20% Asian, 80% Hispanic, 20% non-Hispanic).

Aligned with prior research, our results indicate there is high heterogeneity across persons such that the individual network composition of MDD symptoms is unique from person to person. In addition, our findings also provide support for within-person heterogeneity given that, for most persons, individual symptom networks changed dramatically across the 90 days. This is supported by the observation that 86% of individuals experienced at least one change in their most influential symptom, with the median number of shifts being three over the 90 days. Additionally, the majority of individuals had at least one symptom that acted as both the most and least influential symptom at any given point over the 90-day period.

Taken together, our findings offer further insight into short-term symptom dynamics, suggesting that the composition and driving factors of MDD are not only heterogeneous across persons but also within-persons across time.