The Parasite and Infestation Study

September 24, 2026 updated by: Julia Sheffield, Vanderbilt University Medical Center

Understanding the Experience of Patient-Physician Diagnostic Incongruency: I Know Something is Wrong But No One Believes Me

Many people have evidence of bugs, parasites, and infestation, but are told by others that they cannot find a cause. This distressing and frustrating experience can last for years, as the person seeks answers. The current study aims to understand the experience of these individuals. In a 1-2 hour session over Zoom, the investigators will ask participants questions about their experience, have them complete self-report questionnaires, and ask them to complete a few games on the computer. The investigators' goal is to help characterize and understand individuals with this experience to aid in better treatment and inform recommendations for providers.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

The current study aims to characterize the experiences of people who have evidence of bugs, parasites, and/or infestation but are told by physicians or other professionals (e.g. vets, pest control) that there is nothing wrong. The investigators seek to understand the emotional and cognitive aspects of this experience, through semi-structured interviews, self-report questionnaires, and cognitive tasks. The study will take a few hours and is conducted remotely, allowing for participation regardless of the participant's physical location. There is practically no aggregate information on this experience, with most current information relying on case reports and medical record review. The investigators hope to provide greater insights into this experience to guide support for individuals going through this difficult process.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
25

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • United States
    • Tennessee
      • Nashville, Tennessee, United States, 37212
        • Recruiting
        • Vanderbilt University Medical Center
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years to 70 years (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Sampling Method

Non-Probability Sample

Study Population

Adults with a persistent experience of infestation or parasite that physicians or other professionals report no evidence for.

Description

Inclusion Criteria:

  • Men and women aged 18-70 years old
  • At least 50% certain that they have an active infection/infestation/parasite, despite being told by doctor that they do not
  • Ability to read and speak English
  • Access to a computer or phone for virtual visit
  • No self-reported history of schizophrenia-spectrum disorder

Exclusion Criteria:

  • Active substance use disorder (excluding nicotine and caffeine)
  • History of severe head trauma
  • Current use of antipsychotics
  • Serious medical or neurological illness known to interfere with cognitive functioning
  • Diagnosis of a learning disability or cognitive disorder

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Observational Models: COHORT
  • Time Perspectives: CROSS_SECTIONAL

Cohorts and Interventions

Group / Cohort

Group / Cohort

A group or subgroup of participants in an observational study that is assessed for biomedical or health outcomes.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
PPDI Group
Other: No intervention - observational study

This study will not involve an intervention.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Psychological Wellbeing
Time Frame: Baseline

Total score on the Warwick-Edinburgh Mental Wellbeing Scale (WEMWBS); scores range from 14-70; higher scores reflect greater wellbeing
Baseline
Social Network
Time Frame: Baseline

Ludden Social Network Scale - total score; higher scores reflect larger and closer social network (score: 0-30)
Baseline
Depression
Time Frame: Baseline

Total score - Beck Depression Inventory -II; Scores range from 0-63 with higher scores reflecting worse depression
Baseline
Anxiety
Time Frame: Baseline

Perseverative Thinking Questionnaire (PTQ); scores range from 0-60, higher scores reflect more perseveration
Baseline
Belief Updating
Time Frame: Baseline

Expectations of prior volatility (mu3) calculated from reversal learning task; higher parameter scores reflect greater expectations of volatility
Baseline
BADE
Time Frame: Baseline

Evidence Integration Impairment (EII) will be calculated based on decisions on the Bias Against Disconfirmatory Evidence task. Higher scores reflect more difficulty integrating information
Baseline
Interoceptive Awareness
Time Frame: Baseline

Multidimensional Assessment of Interoceptive Awareness-2; scores range from 0-185; higher scores reflect better interpersonal awareness
Baseline
Dissociation
Time Frame: Baseline

Cernis Felt Sense of Anomaly Scale (CEFSA); scores range from 0-140, higher scores reflect more severe dissociative experiences
Baseline
Childhood Trauma
Time Frame: Baseline

Childhood Trauma Questionnaire (CTQ)- scores range from 5-100, higher scores reflect more severe childhood maltreatment
Baseline
DACOBS
Time Frame: Baseline

Davos Assessment of Cognitive Biases Scale; higher scores reflect more severe cognitive biases. Scores range from 42-294
Baseline

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Vanderbilt University Medical Center

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Julia Sheffield, PhD, Vanderbilt University Medical Center

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
December 31, 2024

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
December 1, 2029

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
December 1, 2030

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
September 18, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 24, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
September 30, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
September 30, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
September 24, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
September 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 201489

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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