Mechanisms and Vulnerabilities in Functional Neurological Disorder.

Functional neurological disorder (FND) is a disabling neuropsychiatric condition characterized by altered voluntary motor or sensory functions and cognitive symptoms. Unlike other neurological disorders, FND is not caused by structural brain damage but by disruptions across brain networks involved in agency, attention, emotion processing, sensory-motor control, and interoception. These alterations align with alterations in predictive coding, which propose that abnormal prior beliefs override sensory input, contributing to symptom generation. Early-life trauma is a significant risk factor, interacting with genetic and epigenetic vulnerabilities that influence emotional regulation, stress sensitivity, and brain connectivity. Psychiatric comorbidities are also common and may affect symptom severity and prognosis. This review synthesizes recent research to clarify the complex mechanisms underlying FND by integrating neurobiological, environmental, and psychological factors. By doing so, we aim to advance the understanding of FND pathophysiology and promote a more comprehensive conceptual framework that highlights the role of individual vulnerability.