This cross-sectional observational case-control study aims to investigate symptoms of sluggish cognitive tempo (SCT), also known as cognitive disengagement syndrome (CDS), in adults diagnosed with Functional Neurological Symptom Disorder/Conversion Disorder (FNSD/CD). The study compares SCT/CDS symptoms between patients with FNSD/CD and healthy controls and evaluates their relationship with clinical variables. It is hypothesized that individuals diagnosed with FNSD/CD will exhibit higher levels of SCT/CDS symptoms compared to healthy controls.

Sluggish Cognitive Tempo (SCT), also referred to as Cognitive Disengagement Syndrome (CDS), is characterized by symptoms such as excessive daydreaming, mental fogginess, lethargy, slowed behavior, confusion, and reduced alertness. Research indicates that SCT/CDS symptoms are distinct from attention deficit hyperactivity disorder (ADHD), although some overlap may occur. Studies suggest that SCT/CDS may be influenced more by environmental and neurocognitive factors than by heritability.

Functional Neurological Symptom Disorder (FNSD), also known as Conversion Disorder (CD), is characterized by neurological symptoms that cannot be explained by an identifiable neurological disease. These symptoms may include motor dysfunction (weakness, tremor, gait abnormalities), non-epileptic seizures, sensory disturbances, or mixed presentations. Although symptoms are not attributable to structural neurological pathology, they cause significant functional impairment.

The etiology of FNSD remains unclear. Proposed mechanisms include altered functional connectivity between emotional processing networks and motor/sensory regions, impaired memory and attention processing, and stress-related neurobiological dysregulation. Neurocognitive models suggest that attention and memory impairments may be present in individuals with FNSD, particularly under stress.

Despite increasing research on SCT/CDS in ADHD and other psychiatric conditions, SCT/CDS symptoms have not been systematically studied in adults with FNSD. Considering the hypothesized cognitive and attentional involvement in FNSD, SCT/CDS symptoms may be present in this population.

This study is designed as a cross-sectional case-control study conducted at the Psychiatry Outpatient Clinic of Elazığ Mental Health and Diseases Hospital. Participants will include adults aged 18-65 years diagnosed with FNSD according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision criteria and a matched healthy control group without psychiatric diagnoses.

Participants will complete a sociodemographic and clinical information form and validated psychometric scales, including: Barkley's Adult Sluggish Cognitive Tempo Scale (Turkish version), Somatoform Dissociation Questionnaire, Adult ADHD Self-Report Scale. No invasive or interventional procedures will be performed. Group comparisons will be conducted using appropriate parametric or non-parametric tests. Correlation and regression analyses will be performed when necessary. Statistical significance will be defined as p ≤ 0.05. Power analysis indicates that a minimum of 24 participants per group (total n=48) is required to achieve 80% power at alpha=0.05.

• Inclusion Criteria for the Functional Neurological Symptom Disorder (FNSD) Group:

  1. Meeting the diagnostic criteria for FNSD/CD according to DSM-5-TR at the time of admission
  2. Being between 18-65 years of age
  3. Absence of additional psychiatric disorders
  4. Absence of alcohol/substance use disorder
  5. Absence of neurological disorders affecting cognition
  6. Being in remission with FNSD/CD
  7. Completing sociodemographic data fully
  8. Willingness to complete the forms and scales.
  9. Willingness to participate in the study

• Exclusion Criteria for the FNSD Group:

  1. Being under 18 or over 65 years of age
  2. Not meeting the diagnostic criteria for FNSD/CD according to DSM-5-TR
  3. Active alcohol/substance use
  4. Having neurological diseases affecting cognitive functions (such as Alzheimer's disease, delirium, Parkinson's disease)
  5. Not being willing to participate in the study
  6. Incomplete sociodemographic data
  7. Not being willing to complete forms and scales.

• Inclusion Criteria for the Healthy Control (HC) Group

  1. Being between 18-65 years of age
  2. Not having any psychiatric disorder
  3. Not having an alcohol/substance use disorder
  4. Not having a neurological disorder affecting cognition
  5. Completing sociodemographic data in full
  6. Being willing to complete the forms and scales.
  7. Being willing to participate in the study

• Exclusion Criteria for the HC Group:

  1. Being under 18 or over 65 years of age
  2. Having a psychiatric disorder
  3. Active alcohol/substance use
  4. Having neurological diseases affecting cognitive functions (such as Alzheimer's disease, delirium, Parkinson's disease)
  5. Not being willing to participate in the study
  6. Incomplete sociodemographic data
  7. Not being willing to complete forms and scales.

The study population will consist of adult participants aged 18-65 years. The Functional Neurological Symptom Disorder (FNSD) group will include consecutive subjects diagnosed with FNSD according to DSM-5-TR criteria who will be admitted to the psychiatry clinic of Elazığ Mental Health and Diseases Hospital (Turkey). The healthy control (HC) group will consist of individuals from the general population who will apply to the hospital medical board and will have no current or past psychiatric or significant medical disorders. All participants will provide informed consent prior to enrollment.

Deidentified individual participant data (IPD) underlying the results reported in this study [Barkley's Adult Sluggish Cognitive Tempo Scale (Turkish version), Somatoform Dissociation Questionnaire, Adult Attention-Deficit/Hyperactivity Disorder Self-Report Scale] will be made available to qualified researchers upon reasonable request for academic purposes. Data will be shared after removal of all direct identifiers and in accordance with applicable ethical approvals and data protection regulations. Access to the data will require a methodologically sound research proposal and a data use agreement. Requests should be directed to the corresponding author.

Data will be available beginning 6 months after publication and will remain available for 5 years.

Access will be granted to researchers who provide a methodologically sound proposal. Requests must be approved by the principal investigator and may require a data use agreement in accordance with institutional and ethical regulations.