Functional Neurological Disorders (FND) represent genuine involuntary neurological symptoms and signs including seizures, weakness and sensory disturbance which have characteristic clinical features, and represent a problem of voluntary control and perception despite normal basic structure of the nervous system. The historical view of FND as a diagnosis of exclusion can lead to unnecessary healthcare resource utilisation, and high direct and indirect economic costs. A systematic review was performed using PRISMA guidelines in order to assess these economic costs, and to assess for any cost- effective treatments.

Methods We searched electronic databases (Pubmed, PsycInfo, Medline, EMBASE, and the National Health Service Economic Evaluations Database of the University of York) for original, primary research publications between inception of the databases and 8^th April 2022. Key search terms included ‘functional neurological disorder’, ‘conversion disorder’ and ‘functional seizures’. Reviews, case reports, case series and qualitative studies were excluded. We performed a descriptive and qualitative thematic analysis of the resulting studies.

Results The search resulted in a total of 3,244 studies. A hand-search of conference abstracts was also conducted. 16 studies were included after screening, and exclusion of duplicates. These included: cost-of-illness (COI) studies which were conducted alongside cohort studies without intervention, which included a comparator group, e.g. another neurological disorder (n=4); COI studies which were conducted alongside cohort studies without intervention, which did not include a comparator group (n=4); economic Evaluations (EE) of interventions which were either pre-post cohort studies (n=6) or randomized controlled trials (n=2). Of these, five studies assessed active interventions, and three studies assessed costs before and after a definitive diagnosis of FND.

Studies showed an excess cost associated with FND, which consisted of both direct, but also large indirect costs. Studies showed promise that interventions, including provision of a definitive diagnosis, could reduce this cost. No cost-effective treatments were identified. Study comparison was limited by study design and location heterogeneity.

Conclusion FND is associated with significant use of healthcare resources, resulting in economic costs to both the patient and the tax-payer, as well as intangible losses. Interventions, including accurate diagnosis, appear to offer an avenue towards reducing these costs.