Pain-related disability in functional neurological disorder (FND): the role of pain intensity and psychological factors

BACKGROUND: Functional neurological disorder (FND) is a complex neurological condition characterised by involuntary motor and sensory symptoms, linked to alterations in brain network functioning rather than abnormalities in brain structure. Pain is common in FND and is associated with reduced quality of life (QoL), distress, and increased disability. The Fear-Avoidance Model (FAM) posits that psychological factors can exacerbate pain and disability. This study aimed to examine whether pain intensity and psychological factors of the FAM predict pain-related disability in individuals with FND. A secondary aim was to assess whether the relationship between pain intensity and pain-related disability was sequentially mediated by pain catastrophising, pain-related avoidance, and depression. METHODS: A total of 248 adults with FND and pain (18-73 years) completed an online cross-sectional survey. Hierarchical regression analysis assessed whether pain intensity and psychological variables predicted pain-related disability. Sequential mediation analysis investigated direct and indirect effects. RESULTS: Eighty-nine percent of participants reported pain associated with FND, and 93.5% reported persistent pain. Pain intensity, pain catastrophising, and pain-related avoidance explained 58.1% of the variance in pain-related disability. Mediation analysis revealed a significant direct effect of pain intensity on pain-related disability, with partial and sequential indirect effects via psychological variables. The final model explained 61.5% of the variance in pain-related disability. CONCLUSION: Participants with FND reported high levels of pain intensity, pain-related disability, and low QoL. These findings highlight the complex interplay between pain and psychological factors in FND, which may be important targets for intervention.