Conversion disorder/functional neurological disorder - a narrative review on current research into its pathological mechanism

Background and objectives: Conversion disorder/functional neurological disorder (CD/FND) can be a chronic disorder and has an unknown pathology. This review explored the current level of research and understanding the origin of CD/FND pathology. Methods: This narrative review collated relevant papers and articles identified by a search in both Scopus and PubMed. Systematic reviews and observational articles focusing on inflammation and childhood trauma were included. Articles that were not in English, case reports, or that included participants from military background, were excluded. Results: Overall 54 papers were included from an initial search number of 5264. 34 of these articles were identifying and discussing new trends and theories related to the pathophysiology while the remaining 20 were defining the current knowledge of CD/FND. There is no definitively known pathophysiology of FND, with several noted categories of involved being immune system, inflammation and neural changes. Each system and mechanism could either be seen as a direct mechanism of action or an indirect effect from a further unknown mechanism of action. Additionally, there seems to be a lack of coherency between these different proposed theories, with little information bringing them together. Further research may explore whether or not inflammation plays a direct role in the pathophysiology of the disorder, and if a difference in the symptoms is dictated by different inflammatory markers. Conclusion: Overall this narrative review identified and postulated different mechanisms for the pathology of CD/FND while also discovering where new research should focus. (C) 2020 Asociacion Universitaria de Zaragoza para el Progreso de la Psiquiatria y la Salud Mental. Published by Elsevier Espana, S.L.U. All rights reserved.