Understanding Hallucinations (Part I)

Study Overview
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Brief Summary
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Psychotic symptoms (hallucinations and delusions) are present in several psychiatric and neurological disorders as well as in the general population. Effective treatment strategies for these symptoms in all patients are lacking and treatment-response can presently not be predicted. To date, the exact pathophysiological mechanism of these symptoms remains unknown. By investigating (subtypes) of hallucinations and delusions in all populations, a common pathway may be found, leading to more effective treatment options. Alternatively, different subtypes may be associated with different pathophysiological mechanisms.

Official Title
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Understanding Hallucinations (Part I) - Phenomenology and Cognition

Conditions
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Hallucinations, No Hallucinations

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: age > 18 years mentally competent in case of delirium: family member able to give informed consent Individuals with hallucinations will have to experience at least one episode of hallucinations over the last month. Individuals without hallucinations: no current hallucinations and a history of maximum 1 episode of hallucinations with a maximum duration of 1 week, at least two years ago. Exclusion Criteria: Age <18) Participants that cannot read, speak or understand Dutch For all included diagnostic groups except delirium: Mentally incompetent individuals who are not capable to provide informed consent, as determined by their treating physician.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Patients with schizophrenia<br>With and without hallucinations | |
| Patients with borderline personality disorder<br>With and without hallucinations | |
| Patients with hearing impairment<br>With and without hallucinations | |
| Patients with visual loss<br>With and without hallucinations | |
| Patients with Parkinson's Disease<br>With and without hallucinations | |
| Patients with Alzheimer's Disease<br>With and without hallucinations | |
| Patients with dementia with Lewy Bodies<br>With and without hallucinations | |
| Patients with Posttraumatic Stress Disorder<br>With and without hallucinations | |
| Patients with delirium<br>With and without hallucinations | |
| Healthy participants<br>With and without hallucinations | |
| Patients with mood disorder<br>With and without hallucinations | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The number of clusters of patients with shared symptom profiles as determined by latent class analysis, and the difference in scores on cognitive assessment between these identified clusters. |  | Three years | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The internal consistency, test-retest reliability, inter-rater reliability, criterion validity and construct validity of a newly developed questionnaire. |  | Two years | 
| The difference in scores on cognitive assessment between participant groups with and without psychotic symptoms. |  | Three years |