Dissociation as a candidate mechanism in functional neurological disorder: Evidence from digital remote monitoring in everyday life

This is the authors' abstract. We don't add key points for this paper.

Background: Affective hyperarousal and dissociation are possible mechanisms underlying symptom occurrence in functional neurological disorder (FND), although evidence is limited by retrospective and cross-sectional measurement. We aimed to examine these mechanisms in everyday life with digital remote monitoring technologies in functional seizures (FS) and functional motor symptoms (FMS).Methods: Smartphone-based ecological momentary assessment (EMA) tracked subjective functional neurological symptoms (FNS), subjectively significant daily events, affect, dissociation, and subjective arousal six times daily over 14 days, alongside wearable heartrate monitoring (Fitbit Charge 5). Participants were aged 18-65 years with FS (n=45) or FMS (n=48). Healthy (HC, n=45) and clinical controls with anxiety/depressive disorders (CC=47) were included for comparison. We used linear mixed-effects models to compare groups and to interrogate concurrent and time-lagged temporal relationships between variables. Results: FS and FMS groups reported elevated dissociation across the 14 days compared to CC/HC (p≤0.01), including depersonalisation, derealisation, and amnesia (p<0.05). Reduced event-related pleasantness was also reported by FS/FMS/CC groups compared to HC (p<0.05). At the day- and momentary-levels, dissociation was the most robust correlate and/or temporal predictor of FNS severity in the FS/FMS groups (p=0.02-<0.001), withstanding correction for confounds. Event-related stress/pleasantness ratings, negative affect, and subjective arousal significantly predicted FNS severity in some models.Conclusions: Dissociation is a distinguishing feature in FS/FMS and a prominent correlate and momentary temporal predictor of FNS severity in both groups, indicating a possible shared mechanism. Future studies should examine the neurobiological basis of dissociation-FNS interactions and explore interventions that enhance management of dissociative states in this population.