Momentary Predictors of Dissociation in Functional Neurological Disorder: An Ecological Momentary Assessment-Based Study

Introduction: Evidence suggests that dissociation may play a role in the manifestation of functional neurological disorder (FND). Dissociative experiences are frequently reported in FND, yet their dynamic associations with affective and physiological states remain underexplored. This study aimed to examine dissociative symptoms in daily life in FND, to identify predictors of dissociation using ecological momentary assessment (EMA) combined with wearable heart-rate monitoring.Methods: Seventeen individuals with FND (functional seizures/motor symptoms) and seventeen age- and gender-matched healthy controls completed EMA via pseudorandom smartphone prompts eight times daily for one week. Dissociation (depersonalisation, derealisation, amnesia), negative affect, and subjective arousal were assessed using items modified from validated scales, while heart-rate was continuously recorded via Fitbit devices. Data were aggregated at week-level for between-group comparisons and analysed using Mann-Whitney U tests. Multilevel modelling was conducted to examine momentary associations between predictors (negative affect, subjective arousal, heart-rate) and dissociative symptoms within the FND group. Time-lagged analyses explored temporal relationships between the predictors and dissociative symptoms.Results: The FND group reported significantly higher dissociative symptoms across the week compared to controls: amnesia (U=63, p=0.004), depersonalisation (U=63.5, p=0.004), and derealisation (U=84, p=0.034). Effect sizes were moderate-large for amnesia and depersonalisation (r=0.56), and small-moderate for derealisation (r=0.42). Negative affect (p-values=