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Incidence and prevalence of psychogenic nonepileptic seizures (functional seizures): a systematic review and an analytical study.

Aim: Psychogenic nonepileptic seizures (PNES) or functional seizures are universal phenomena. However, data on their epidemiology is limited. The aim of the current study was to review the literature on the epidemiology of PNES and to provide analytical estimates of its incidence and prevalence based on the direct data that are available from previous studies on PNES.Methods: The methods of this work had two parts: 1) MEDLINE, PsycINFO, and Scopus from inception to October 19, 2019 were systematically searched. 2) The analytical study of the incidence and prevalence of PNES was performed, based on the following data from previous studies: incidence of PNES, duration of PNES before making a diagnosis, outcome and mortality of PNES.Results: The search strategy yielded five articles; three were on the incidence and two on the prevalence. In the analytical part of the study, the incidence of PNES was calculated to be 3.1 (95% Confidence Interval: 1.1 to 5.1) per 100,000 population per year. The calculated prevalence rate of PNES in 2019 was 108.5 (95% Confidence Interval: 39.2 to 177.8) per 100,000 population, in the USA.Conclusion: While, the generalizability of these calculated incidence and prevalence rates to other places in the world is limited, they give us a reasonable hint that PNES is a common condition and the prevalence is much more than that it was thought before.