# Prevalence and impact of comorbid PTSD, c-PTSD and EUPD on symptom severity in functional neurological disorder: protocol for a systematic review and meta-analysis

## TL;DR

This study will review how often PTSD, c-PTSD, and EUPD occur in people with functional neurological disorder and how these conditions affect symptom severity.

## Contribution

The study introduces a systematic review and potential meta-analysis to quantify the prevalence and impact of trauma-related comorbidities in FND.

## Key findings

- The review will establish current prevalence rates of PTSD, c-PTSD, and EUPD in FND populations.
- It will compare symptom severity in FND patients with and without these comorbid conditions.
- Findings will inform trauma-informed treatment strategies for FND.

## Abstract

Previous trauma and adverse life experiences have been hypothesised to be aetiological factors for functional neurological disorder (FND) leading to the hypothesis of a ‘trauma-subtype’ of FND. Individuals who have experienced prior abuse are more likely to develop FND than healthy controls. Post-traumatic stress disorder (PTSD) and personality disorders have been described to be comorbid with FND at varying prevalence rates. Complex PTSD (c-PTSD) and emotionally unstable personality disorder (EUPD) have clinical similarities with PTSD and trauma is a common aetiological factor in the development of all three conditions. There is some research exploring the resemblance of personality traits in populations diagnosed with FND and EUPD compared with controls. However, it remains unclear what the current prevalence rates are of PTSD, c-PTSD and EUPD in populations diagnosed with FND. Understanding the overlap between these trauma-based comorbid psychiatric diagnoses with FND will hopefully inform better and more comprehensive trauma-informed treatment strategies. The aims of the systematic review are therefore to (1) establish the prevalence of PTSD, c-PTSD and EUPD in adults diagnosed with FND and (2) compare core FND symptom severity between adults with FND alone and those with comorbid PTSD, c-PTSD and EUPD.

This systematic review will assess the prevalence of PTSD, c-PTSD and EUPD in FND patients aged over 18, diagnosed using standardised questionnaires or clinical interviews as per international diagnostic criteria. Studies will be identified through comprehensive searches of databases including PsycINFO, PsycARTICLES, CINAHL, MEDLINE, EMBASE, Web of Science and Scopus, from May 1990 to May 2025. The review aims to estimate the prevalence of these conditions in FND, with findings presented as a narrative description discussing contributing factors, and a meta-analysis considered if heterogeneity is suitable.

Ethical approval is not required since only data from existing studies will be used and no original data will be collected. Results will be disseminated at national and international academic conferences and in peer-reviewed publications. Any deviations from this protocol will be recorded and explained in the final report and updated on PROSPERO.

CRD42024599112.