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=<0.001, β=0.094-0.111), subjective arousal (p-values=<0.001, β=0.102-0.124), and heart-rate (p-values=0.01-0.006, β= 0.078-0.091) were each significant concurrent predictors of all three dissociative symptom types. In combined models, negative affect and subjective arousal remained robust predictors across all symptom domains, whereas heart-rate lost significance. Time-lagged analyses did not yield significant associations.Conclusion: Individuals with FND report elevated dissociative symptoms compared to healthy controls. Dissociation was consistently associated with subjective arousal and negative affect, but not heart-rate, underscoring the importance of subjective emotional states over physiological influences on dissociative symptom variability. The absence of temporal effects highlights the transient nature of dissociation in FND. These findings support conceptualising FND through a dissociative lens and emphasise the need for larger longitudinal studies to clarify mechanisms and inform tailored interventions.