Momentary predictors of dissociation in functional neurological disorder: an ecological momentary assessment-based pilot 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 pilot 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. This was a secondary analysis of data from a pilot case-control intensive longitudinal observation study. 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. Multilevel modelling was conducted to examine between-group differences, and 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 (F(1,34)=13.09, p <.001), depersonalisation (F(1, 34)=7.35, p = .010), and derealisation (F(1, 34)=8.31, p = .007), these differences withstood correction for anxiety, but not for depression. Negative affect ( p-values =<0.001, β=0.094-0.111), subjective arousal ( p-values =<0.001, β=0.102-0.124), and higher 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 self-reported elevated dissociative symptoms in daily life compared to healthy controls; however, these significant differences did not remain when controlling for depression. 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 self-reported dissociative symptom variability. The absence of temporal effects highlights the transient nature of dissociation in FND. These findings support the possibility of conceptualising FND through a dissociative lens and emphasise the need for larger longitudinal studies to clarify underlying mechanisms.