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    1. Verbal Fluency TestGradeA
    2. Stroop Color-Word TestGradeA
    3. Trail Making TestGradeA
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    • Cognitive outcomes, 2026

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    Registered studies

    • Dementia and Alzheimer's1,673
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    16,361Registered studies name a cognitive test in an outcome measure11,688 name a test you can run hereExplore the studies
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  1. Home
  2. /Data
  3. /Clinical trials
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  5. /Parkinson's disease

Clinical trials data

Cognitive tests in Parkinson's disease trials: 892 registered studies

Every registered Parkinson's disease study on ClinicalTrials.gov that names a cognitive test in an outcome measure: the tests used most, how often as a primary outcome, which tests go together, how large the studies are and when they measure the outcome.

Registered Parkinson's disease studies name a cognitive test in an outcome
892
Name one in a primary outcome
276
See the tests
Median participants per study
49
By phase
Led by industry
86

The tests Parkinson's disease trials use most

The Trail Making Test leads: 156 of the 892 studies name it, 17%. Next comes Verbal Fluency (140). As a primary outcome, Verbal Fluency leads with 45 studies.

  1. 1

    Trail Making Test156 studies, 38 as a primary outcome

  2. 2

    Verbal Fluency140 studies, 45 as a primary outcome

  3. 3

    Stroop Color-Word Test126 studies, 39 as a primary outcome

  4. 4

    Digit Span Test86 studies, 15 as a primary outcome

  5. 5

    Verbal Learning61 studies, 22 as a primary outcome

  6. 6

    Category Fluency44 studies, 13 as a primary outcome

  7. 7

    Symbol Coding41 studies, 10 as a primary outcome

  8. 8

    Picture Naming Test37 studies, 7 as a primary outcome

  9. 9

    Clock Drawing Task33 studies, 10 as a primary outcome

  10. 10

    Line Angle Matching25 studies, 6 as a primary outcome

  11. 11

    Finger Tapping Task24 studies, 8 as a primary outcome

  12. 12

    Card Sorting Test (Berg)23 studies, 6 as a primary outcome

  13. 13

    Complex Figure Copy and Recall21 studies, 5 as a primary outcome

  14. 14

    Go/No-Go Task18 studies, 8 as a primary outcome

  15. 15

    Choice Reaction Time15 studies, 11 as a primary outcome

  16. 16

    Simple Reaction Time14 studies, 6 as a primary outcome

  17. 17

    Task Switching Test14 studies, 5 as a primary outcome

  18. 18

    Matrix Reasoning14 studies, 4 as a primary outcome

  19. 19

    N-Back Task13 studies, 4 as a primary outcome

  20. 20

    Tower Planning13 studies, 4 as a primary outcome

  21. 21

    Short Story Recall11 studies, 4 as a primary outcome

  22. 22

    Stop-Signal Task10 studies, 6 as a primary outcome

  23. 23

    Eriksen Flanker Task10 studies, 4 as a primary outcome

  24. 24

    Psychomotor Vigilance Task10 studies, 2 as a primary outcome

  25. 25

    Delayed Recall Module9 studies, 2 as a primary outcome

A test as a primary outcomeOnly in secondary or other outcomes

47% of Parkinson's disease studies name only instruments outside the library, such as clinician-administered screening scales. They count in every figure on this page and are not listed. The explorer below holds all 93 tests.

Tests used together

The pairs of tests Parkinson's disease studies name together most often.
  1. Stroop Color-Word Test and Trail Making Test68 studies name both
  2. Trail Making Test and Verbal Fluency50 studies name both
  3. Digit Span Test and Verbal Fluency43 studies name both
  4. Digit Span Test and Trail Making Test42 studies name both
  5. Stroop Color-Word Test and Verbal Fluency42 studies name both
  6. Digit Span Test and Stroop Color-Word Test37 studies name both
  7. Verbal Fluency and Verbal Learning33 studies name both
  8. Trail Making Test and Verbal Learning32 studies name both
  9. Category Fluency and Verbal Fluency29 studies name both
  10. Picture Naming Test and Verbal Fluency25 studies name both

Studies by start year

Each study counted once. 2026 is partly planned starts.
01002000: 0 studies, 0 with a test as a primary outcome20002001: 0 studies, 0 with a test as a primary outcome2002: 0 studies, 0 with a test as a primary outcome2003: 2 studies, 0 with a test as a primary outcome2004: 1 studies, 0 with a test as a primary outcome2005: 0 studies, 0 with a test as a primary outcome20052006: 2 studies, 0 with a test as a primary outcome2007: 6 studies, 3 with a test as a primary outcome2008: 1 studies, 0 with a test as a primary outcome2009: 9 studies, 5 with a test as a primary outcome2010: 8 studies, 4 with a test as a primary outcome20102011: 19 studies, 6 with a test as a primary outcome2012: 21 studies, 6 with a test as a primary outcome2013: 28 studies, 6 with a test as a primary outcome2014: 24 studies, 5 with a test as a primary outcome2015: 25 studies, 13 with a test as a primary outcome20152016: 31 studies, 8 with a test as a primary outcome2017: 48 studies, 13 with a test as a primary outcome2018: 49 studies, 13 with a test as a primary outcome2019: 57 studies, 23 with a test as a primary outcome2020: 69 studies, 17 with a test as a primary outcome20202021: 80 studies, 29 with a test as a primary outcome2022: 64 studies, 21 with a test as a primary outcome2023: 76 studies, 22 with a test as a primary outcome2024: 82 studies, 23 with a test as a primary outcome2025: 88 studies, 26 with a test as a primary outcome20252026: 100 studies, 33 with a test as a primary outcome

A test as a primary outcomeOnly in secondary or other outcomes

Show as a table
Registered studies by start year
Start yearStudiesA test as a primary outcome
200000
200100
200200
200320
200410
200500
200620
200763
200810
200995
201084
2011196
2012216
2013286
2014245
20152513
2016318
20174813
20184913
20195723
20206917
20218029
20226421
20237622
20248223
20258826
202610033

Phases and sponsors

By phase

  • Early phase 110 studies, 1 as a primary outcome
  • Phase 134 studies, 5 as a primary outcome
  • Phase 1/222 studies, 9 as a primary outcome
  • Phase 291 studies, 13 as a primary outcome
  • Phase 2/36 studies, 1 as a primary outcome
  • Phase 321 studies, 6 as a primary outcome
  • Phase 432 studies, 11 as a primary outcome
  • Not applicable509 studies, 153 as a primary outcome
  • Observational167 studies, 77 as a primary outcome

Sponsors and study types

Lead sponsor: industry 86, NIH 3, universities, hospitals and others 803. Interventional 725, observational 167.

Status, results, interventions and countries

Status

  • Recruiting196 studies, 69 as a primary outcome
  • Not yet recruiting56 studies, 19 as a primary outcome
  • Active, not recruiting33 studies, 14 as a primary outcome
  • Completed392 studies, 121 as a primary outcome
  • Stopped early54 studies, 16 as a primary outcome
  • Status unknown161 studies, 37 as a primary outcome

What they test

  • Behavioral153 studies, 51 as a primary outcome
  • Drug195 studies, 42 as a primary outcome
  • Device209 studies, 56 as a primary outcome
  • Dietary supplement22 studies, 4 as a primary outcome
  • Procedure41 studies, 9 as a primary outcome
  • Diagnostic test31 studies, 15 as a primary outcome
  • Biological16 studies, 3 as a primary outcome
  • Radiation5 studies, 3 as a primary outcome
  • Combination product1 studies, 1 as a primary outcome
  • Genetic9 studies, 4 as a primary outcome
  • Other241 studies, 88 as a primary outcome
  • None given76 studies, 38 as a primary outcome

Intervention types as registered. A study can list several; observational studies often list none.

Where their sites are

  • United States265 studies, 101 as a primary outcome
  • Italy74 studies, 29 as a primary outcome
  • China71 studies, 15 as a primary outcome
  • Canada61 studies, 16 as a primary outcome
  • France58 studies, 11 as a primary outcome
  • United Kingdom49 studies, 6 as a primary outcome
  • Türkiye47 studies, 21 as a primary outcome
  • Germany40 studies, 4 as a primary outcome
  • Spain37 studies, 12 as a primary outcome
  • Netherlands36 studies, 5 as a primary outcome
  • Brazil28 studies, 8 as a primary outcome
  • Switzerland28 studies, 7 as a primary outcome

50 countries in all. A study with sites in several counts in each; 42 list no site.

Reported results

Completed studies with results posted on ClinicalTrials.gov, a results paper the registry links to the study, or both.

Completed Parkinson's disease studies: 170 of 392, 43%

Every completed study with a cognitive outcome: 3,626 of 7,953, 46%

Completed Parkinson's disease studies and every completed study, by how they reported results
ResultsCompleted Parkinson's disease studiesEvery completed study
Results on ClinicalTrials.gov and a paper36, 9%776, 10%
Results on ClinicalTrials.gov only58, 15%1,139, 14%
A results paper only76, 19%1,711, 22%
Neither222, 57%4,327, 54%

How many participants they enroll

Enrollment as registered: actual for a finished study, planned for one still recruiting.
102050100200500
  • Phase 116 median, 9 to 24
  • Phase 1/217 median, 13 to 40
  • Phase 260 median, 31 to 100
  • Phase 3130 median, 80 to 410
  • Phase 421 median, 17 to 56
  • Not applicable44 median, 25 to 80
  • Observational100 median, 50 to 221
Participants per study. The bar spans the middle half of the studies in each phase, the mark is the median, and the axis is logarithmic. Phases with fewer than 10 studies that give a size are left out.
Show as a table
Participants per Parkinson's disease study by phase
PhaseStudies with a sizeMedianMiddle half
Phase 130169 to 24
Phase 1/2211713 to 40
Phase 2886031 to 100
Phase 32113080 to 410
Phase 4322117 to 56
Not applicable5044425 to 80
Observational16310050 to 221

When the cognitive outcome is measured

Half of the primary outcomes that name a library test are measured within 6 weeks of the start, and the middle half from the first day to 14 weeks. 312 primary outcomes give a duration.

Latest time point of each outcome

  • Within a day207 outcomes, 97 as a primary outcome
  • Up to 4 weeks187 outcomes, 51 as a primary outcome
  • 1 to 3 months318 outcomes, 79 as a primary outcome
  • 3 to 6 months168 outcomes, 42 as a primary outcome
  • 6 to 12 months78 outcomes, 19 as a primary outcome
  • 1 to 2 years49 outcomes, 9 as a primary outcome
  • Over 2 years51 outcomes, 15 as a primary outcome
  • No duration given58 outcomes, 24 as a primary outcome

A test as a primary outcomeOnly in secondary or other outcomes

1,058 of the 1,116 outcome measures give a duration. A single visit counts as within a day.

Median time to the primary outcome, by test

Median weeks to the latest time point of each test's primary outcomes
TestPrimary outcomesMedian
Verbal Fluency4012 weeks
Stroop Color-Word Test388 weeks
Trail Making Test366 weeks
Verbal Learning2011 weeks
Digit Span Test154 weeks
Category Fluency114 weeks
Choice Reaction Time108 weeks

Explore the Parkinson's disease studies

The 475 Parkinson's disease studies that name a test in the library, with filters for test, phase, sponsor, status, country, intervention, outcome list, size and start year. Each study links to its record on ClinicalTrials.gov.
ConditionParkinson's disease

475 studies match. 183 name a library test in a primary outcome. Median size 45 participants. Median time to the primary outcome: 6 weeks.

Loading 475 studies; the filters turn on when they arrive.

By start year
02040602000: 0 studies, 0 naming a library test in a primary outcome20002001: 0 studies, 0 naming a library test in a primary outcome2002: 0 studies, 0 naming a library test in a primary outcome2003: 2 studies, 0 naming a library test in a primary outcome2004: 1 studies, 0 naming a library test in a primary outcome2005: 0 studies, 0 naming a library test in a primary outcome20052006: 1 studies, 0 naming a library test in a primary outcome2007: 5 studies, 3 naming a library test in a primary outcome2008: 1 studies, 0 naming a library test in a primary outcome2009: 7 studies, 4 naming a library test in a primary outcome2010: 5 studies, 4 naming a library test in a primary outcome20102011: 13 studies, 6 naming a library test in a primary outcome2012: 11 studies, 5 naming a library test in a primary outcome2013: 16 studies, 5 naming a library test in a primary outcome2014: 15 studies, 4 naming a library test in a primary outcome2015: 12 studies, 5 naming a library test in a primary outcome20152016: 16 studies, 5 naming a library test in a primary outcome2017: 25 studies, 8 naming a library test in a primary outcome2018: 29 studies, 8 naming a library test in a primary outcome2019: 33 studies, 15 naming a library test in a primary outcome2020: 30 studies, 13 naming a library test in a primary outcome20202021: 42 studies, 18 naming a library test in a primary outcome2022: 33 studies, 11 naming a library test in a primary outcome2023: 40 studies, 17 naming a library test in a primary outcome2024: 37 studies, 19 naming a library test in a primary outcome2025: 40 studies, 10 naming a library test in a primary outcome20252026: 60 studies, 23 naming a library test in a primary outcome

2026 is partly planned starts. Not shown: 1 with no start year.

Show as a table
Matching studies by start year
Start yearStudiesAs a primary outcome
200000
200100
200200
200320
200410
200500
200610
200753
200810
200974
201054
2011136
2012115
2013165
2014154
2015125
2016165
2017258
2018298
20193315
20203013
20214218
20223311
20234017
20243719
20254010
20266023

Library tests named most

Largest condition groups

  • Parkinson's disease475 studies, 183 as a primary outcome
  • Dementia and Alzheimer's41 studies, 20 as a primary outcome
  • Mild cognitive impairment33 studies, 12 as a primary outcome
  • Aging, frailty and exercise23 studies, 10 as a primary outcome
  • Sleep and sleep disorders17 studies, 6 as a primary outcome
  • Stroke16 studies, 2 as a primary outcome
  • Depression and bipolar disorder14 studies, 5 as a primary outcome
  • Multiple sclerosis12 studies, 2 as a primary outcome
  • Healthy volunteers10 studies, 6 as a primary outcome
  • Anxiety, PTSD and OCD6 studies, 1 as a primary outcome
  • Pain and fatigue6 studies, 1 as a primary outcome
  • Schizophrenia and psychosis5 studies, 2 as a primary outcome

Phases

Participants

Lead sponsor: industry 33, NIH 1, other 441. Interventional 403, observational 72.

As a primary outcomeSecondary or other outcome

The studies, newest registration first

Each number opens the study's record on ClinicalTrials.gov.

Registered studies that match the filters, newest registration first, with the library tests each one names and the outcome list that names them.
StudyStartPhaseConditionsParticipantsLead sponsorStatusLibrary tests named, with the latest time point
NCT07907718Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants50Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Trail Making TestPrimary8 weeks
  • Stroop Color-Word TestPrimary8 weeks
  • Go/No-Go TaskPrimary8 weeks
NCT07886450Start2026PhaseObservationalConditionsParkinson's diseaseParticipants128Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Antisaccade TaskPrimarysame day
NCT07882108Start2025PhaseNot applicableConditionsParkinson's disease, Sleep and sleep disordersParticipants72Lead sponsorOtherStatusRecruitingLibrary tests named
  • Category FluencyOther outcome12 weeks
NCT07865260Start2026PhaseNot applicableConditionsMild cognitive impairment, Stroke, Parkinson's diseaseParticipants80Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Trail Making TestSecondary8 weeks
  • Stroop Color-Word TestSecondary8 weeks
  • Corsi Block-Tapping TestSecondary8 weeks
NCT07860294Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants120Lead sponsorOtherStatusRecruitingLibrary tests named
  • Stroop Color-Word TestSecondary6 months
NCT07846007Start2024PhaseNot applicableConditionsParkinson's diseaseParticipants15Lead sponsorOtherStatusRecruitingLibrary tests named
  • Stop-Signal TaskPrimarysame day
NCT07838675Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants120Lead sponsorOtherStatusRecruitingLibrary tests named
  • Digit Span TestSecondary6 months
  • Word Pair LearningSecondary6 months
NCT07833748Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants12Lead sponsorOtherStatusRecruitingLibrary tests named
  • Trail Making TestSecondary13 weeks
  • Symbol CodingSecondary13 weeks
  • Choice Reaction TimeSecondary13 weeks
  • Simple Reaction TimeSecondary13 weeks
  • Finger Tapping TaskSecondary13 weeks
NCT07832695Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants90Lead sponsorOtherStatusRecruitingLibrary tests named
  • Verbal FluencySecondary8 weeks
  • Digit Span TestSecondary8 weeks
NCT07827963Start2026PhaseObservationalConditionsMild cognitive impairment, Parkinson's diseaseParticipants80Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Corsi Block-Tapping TestPrimary2 years
NCT07824128Start2026PhaseNot applicableConditionsDementia and Alzheimer's, Mild cognitive impairment, Parkinson's diseaseParticipants120Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Alternative Uses TaskPrimary8 months
NCT07815964Start2026PhaseObservationalConditionsParkinson's diseaseParticipants100Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Verbal FluencyPrimary
NCT07813156Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants24Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Stroop Color-Word TestSecondary
  • Digit Span TestSecondary
  • Picture Naming TestSecondary
  • Clock Drawing TaskSecondary
  • Letter-Number Sequencing TaskSecondary
  • Selective Reminding TaskSecondary
  • Line Angle MatchingSecondary
NCT07786116Start2025PhaseNot applicableConditionsDementia and Alzheimer's, Mild cognitive impairment, Parkinson's disease, Sleep and sleep disordersParticipants215Lead sponsorOtherStatusRecruitingLibrary tests named
  • Category FluencyOther outcome18 months
NCT07777419Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants20Lead sponsorOtherStatusRecruitingLibrary tests named
  • Stroop Color-Word TestSecondarysame day
  • Verbal FluencyPrimarysame day
  • Go/No-Go TaskSecondarysame day
  • Category FluencyPrimarysame day
NCT07721688Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants40Lead sponsorOtherStatusRecruitingLibrary tests named
  • Arithmetic Fluency TaskSecondary4 weeks
NCT07718659Start2026PhasePhase 1ConditionsParkinson's diseaseParticipants8Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Trail Making TestSecondary12 months
NCT07714772Start2026PhaseObservationalConditionsParkinson's disease, Sleep and sleep disordersParticipants50Lead sponsorOtherStatusNot yet recruitingLibrary tests named
  • Trail Making TestSecondary2 weeks
  • Symbol CodingSecondary2 weeks
NCT07705373Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants200Lead sponsorOtherStatusRecruitingLibrary tests named
  • Trail Making TestSecondary
NCT07703137Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants40Lead sponsorOtherStatusRecruitingLibrary tests named
  • Arithmetic Fluency TaskSecondary12 weeks
NCT07702929Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants48Lead sponsorOtherStatusRecruitingLibrary tests named
  • Stop-Signal TaskPrimary4 weeks
  • Choice Reaction TimePrimary4 weeks
  • Simple Reaction TimePrimary4 weeks
NCT07678983Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants66Lead sponsorOtherStatusActive, not recruitingLibrary tests named
  • Trail Making TestSecondary8 weeks
  • Stroop Color-Word TestSecondary8 weeks
  • Verbal FluencySecondary8 weeks
  • Digit Span TestSecondary8 weeks
  • Category FluencySecondary8 weeks
NCT07651085Start2024PhaseObservationalConditionsDementia and Alzheimer's, Mild cognitive impairment, Parkinson's disease, Sleep and sleep disordersParticipants65Lead sponsorOtherStatusActive, not recruitingLibrary tests named
  • Verbal LearningPrimary
  • Verbal FluencyPrimary
  • Category FluencyPrimary
  • Clock Drawing TaskPrimary
NCT07641569Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants39Lead sponsorOtherStatusCompletedLibrary tests named
  • Trail Making TestPrimary6 weeks
NCT07641556Start2026PhaseNot applicableConditionsParkinson's diseaseParticipants40Lead sponsorOtherStatusRecruitingLibrary tests named
  • Trail Making TestPrimary6 weeks

Page 1 of 19

Questions, answered from the data

Which cognitive test do Parkinson's disease trials use most?

The Trail Making Test: 156 of the 892 registered studies name it in an outcome measure, 17%. Next come Verbal Fluency (140) and the Stroop Color-Word Test (126).

Which cognitive test do Parkinson's disease trials use most as a primary outcome?

Verbal Fluency, named in a primary outcome by 45 studies. 276 of the 892 studies, 31%, name a cognitive test in a primary outcome.

How many participants does a phase 2 Parkinson's disease trial enroll?

Half of the phase 2 Parkinson's disease studies enroll 60 participants or fewer, and the middle half enroll 31 to 100. 88 of them give a size.

How long after the start do Parkinson's disease trials measure a cognitive outcome?

Half of the primary outcomes that name a library test are measured within 6 weeks of the start, and the middle half from the first day to 14 weeks. 312 primary outcomes give a duration.

Which cognitive tests do Parkinson's disease trials use together?

The Stroop Color-Word Test with the Trail Making Test most often: 68 studies name both. Next, the Trail Making Test with Verbal Fluency (50).

How many completed Parkinson's disease trials have reported results?

170 of the 392 completed Parkinson's disease studies, 43%, have reported results: 94 posted them on ClinicalTrials.gov, 112 have a results paper linked to the registry record, and 36 did both. The other 222 show neither. Of all completed studies with a cognitive outcome, 46% have reported results.

Other conditions

  • Dementia and Alzheimer's79 shared
  • Mild cognitive impairment40 shared
  • Aging, frailty and exercise34 shared
  • Sleep and sleep disorders33 shared
  • Depression and bipolar disorder25 shared
  • Stroke20 shared
  • Multiple sclerosis18 shared
  • Healthy volunteers14 shared
  • Anxiety, PTSD and OCD13 shared
  • Pain and fatigue13 shared
  • Cardiovascular disease8 shared
  • Schizophrenia and psychosis7 shared
  • Brain injury and concussion7 shared
  • Obesity and diabetes6 shared
  • Delirium, surgery and intensive care5 shared
  • Epilepsy5 shared
  • COVID-19 and long COVID4 shared
  • Substance use and addiction3 shared
  • Cancer3 shared
  • Lung disease3 shared
  • Hearing loss1 shared
  • ADHD357 studies
  • Cognitive impairment and decline354 studies
  • Autism200 studies

All 16,361 registered studies, by test, condition, phase and year.

How the studies are counted

For each test family, the census runs ClinicalTrials.gov's own outcome search for the family's names and reads every study first posted by the day the family was counted. These studies were read on 10 November 2026. A study counts once on a page, however many tests it names. Counts for a test cover every version of the task under any of its names, so a page can count studies that used a commercial version.

The census adds two things to each record and changes nothing in it: which outcome list names the test (primary, then secondary, then other), and the condition groups, matched on the study's condition names and MeSH terms. A study can fall in several groups; one whose only condition is cognitive impairment or decline falls in “Cognitive impairment and decline”. Studies that name only instruments outside the library count in every total and share but are not listed.

A second read on 10 November 2026 added each study's overall status, whether results are posted, its intervention types, the countries of its sites and the time frame of the outcome that names each test. A time frame counts by the latest time point it names: “Baseline, 12 and 24 weeks” is 24 weeks, a single visit is within a day, and one that names no duration, such as “end of treatment”, is left out of the timings.

A third read on 10 November 2026 added the papers the registry links to each study: those its sponsor lists as reporting results, and those PubMed links to it through the study's NCT number. A study has a results paper when one of them came out in or after the month of its primary completion and PubMed does not class it as a protocol, review or comment. A paper that never gives the NCT number is not linked, so some studies counted as reporting neither did publish.

Source: ClinicalTrials.gov, a database of the U.S. National Library of Medicine, which does not endorse these pages. Every study line is in the data release 2.1.0, and the explorer's own file is clinical-trials-studies.json.

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