Comorbidities Across Functional Neurological Disorder Subtypes: A Comprehensive Narrative Synthesis.

Area of Science:

• Neurology
• Psychiatry
• Clinical Psychology

Background:

• Functional Neurological Disorder (FND) presents with diverse symptoms (motor, cognitive, seizure-like) not explained by structural neurological disease.
• Comorbid psychiatric and somatic conditions significantly impact FND's clinical course, diagnostic complexity, and treatment outcomes.

Purpose of the Study:

• To systematically investigate psychiatric and medical comorbidities in major FND subtypes: Functional Cognitive Disorder (FCD), Functional Movement Disorder (FMD), and Psychogenic Non-Epileptic Seizures (PNES).
• To identify subtype-specific patterns and shared vulnerabilities in FND comorbidities.

Main Methods:

• Conducted a narrative literature review using systematic principles and PRISMA guidelines.
• Included foundational and contemporary studies on comorbidities in FCD, FMD, PNES, PPPD, and general FND populations.
• Organized extracted data by FND subtype and comorbidity type (psychiatric or medical/somatic).

Main Results:

• High rates of psychiatric comorbidities (depression, anxiety, PTSD, dissociation) were observed across all FND subtypes.
• FCD linked to internalizing symptoms; FMD associated with trauma and emotional dysregulation; PNES showed the highest psychiatric burden.
• Prevalent somatic comorbidities (fibromyalgia, chronic pain, IBS, fatigue) suggest overlapping biopsychosocial mechanisms.

Conclusions:

• Comorbid psychiatric and medical conditions are central to understanding and managing FND.
• Subtype-specific patterns necessitate individualized diagnostic and therapeutic strategies.
• Shared biopsychosocial mechanisms support integrated care models for the FND spectrum.