Differentiating the FP5-8 phenomenological characteristics in major depressive episode in depressive disorder from bipolar disorder: insights from a 14-day Hong Kong ecological momentary assessment study with 4632 observations on affect dynamics, anhedonia, meaning-in-life, and trait moderators

Objectives: Diagnostic accuracy is an unmet need for major depressive disorder (MDD) and major depressive episode (MDE) in bipolar disorder (BD). Although a validated biomarker does not currently exist, phenomenological characteristics may assist in differentiating MDD from MDE in BD. This study aimed to examine phenomenological characteristics of positive affect (PA), its dynamics, and its temporal relationships with pleasure attainment and meaning in life (MIL). Additionally, we examined the moderating roles of mindfulness and grit in the relationship between negative affect (NA) and positive mental health (PMH) across MDD, MDE in BD, and healthy controls using ecological momentary assessment (EMA).

Methods: A total of 88 participants with MDD (n = 29) or MDE in BD (n = 29) and healthy controls (n = 30) completed five EMA assessments daily over 2 weeks, reporting PA, pleasure, MIL, and NA. Trait mindfulness and grit were assessed using the Five Facet Mindfulness Questionnaire and the Short Grit Scale. Multilevel modelling estimated PA dynamics (inertia, variability, and instability) and time-lagged relationships between PA, pleasure, and MIL. Moderation and simple slope analyses explored the effects of NA, mindfulness, and grit on PMH.

Results: From 4632 EMA observations, PA dynamics did not differ across groups (all p > 0.05). All groups had a bidirectional relationship between PA and pleasure. However, in MDE in BD, prior pleasure (β = -0.11, p = 0.025) and PA (β = -0.13, p = 0.025) predicted subsequent MIL less significantly than in MDD and healthy controls. Moreover, lower NA levels strengthened the mindfulness-MIL relationship in MDD (β = -0.340, p = 0.049), whereas higher grit levels attenuated NA’s negative impact on pleasure in BD (β = 0.237, p = 0.046).

Conclusions: Persons with MDE in BD, but not MDD reported less MIL from PA and pleasantness. The differential roles of mindfulness and grit in shaping PMH suggest targeted interventions could enhance well-being in MDD and BD. EMA provides a granular, time-series approach to differentiate mood disorders.