Clinical trials data
Cognitive tests in ADHD trials: 357 registered studies
Every registered ADHD 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 ADHD studies name a cognitive test in an outcome
- 357
- Led by industry
- 50
The tests ADHD trials use most
The Continuous Performance Test leads: 123 of the 357 studies name it, 34%. Next comes the Go/No-Go Task (65). As a primary outcome, the Continuous Performance Test leads with 56 studies.
- 1
Continuous Performance Test123 studies, 56 as a primary outcome
- 2
Go/No-Go Task65 studies, 32 as a primary outcome
- 3
Stroop Color-Word Test61 studies, 22 as a primary outcome
- 4
Digit Span Test58 studies, 24 as a primary outcome
- 5
Stop-Signal Task49 studies, 25 as a primary outcome
- 6
AX Continuous Performance Test36 studies, 0 as a primary outcome
- 7
N-Back Task30 studies, 19 as a primary outcome
- 8
Trail Making Test24 studies, 8 as a primary outcome
- 9
Tower Planning20 studies, 9 as a primary outcome
- 10
Eriksen Flanker Task18 studies, 11 as a primary outcome
- 11
Card Sorting Test (Berg)15 studies, 4 as a primary outcome
- 12
Verbal Fluency12 studies, 6 as a primary outcome
- 13
Attention Network Test11 studies, 6 as a primary outcome
- 14
Letter-Number Sequencing Task11 studies, 6 as a primary outcome
- 15
Matrix Reasoning9 studies, 4 as a primary outcome
- 16
Symbol Scan Task9 studies, 3 as a primary outcome
- 17
Symbol Coding9 studies, 2 as a primary outcome
- 18
Spatial Working Memory8 studies, 6 as a primary outcome
- 19
Corsi Block-Tapping Test8 studies, 3 as a primary outcome
- 20
Delay Discounting8 studies, 2 as a primary outcome
- 21
Verbal Learning8 studies, 2 as a primary outcome
- 22
Choice Reaction Time7 studies, 3 as a primary outcome
- 23
Rapid Visual Information Processing7 studies, 2 as a primary outcome
- 24
Dimensional Change Card Sort6 studies, 3 as a primary outcome
- 25
Iowa Gambling Lite6 studies, 2 as a primary outcome
A test as a primary outcomeOnly in secondary or other outcomes
1% of ADHD 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 91 tests.
Tests used together
- AX Continuous Performance Test and Continuous Performance Test36 studies name both
- Continuous Performance Test and Digit Span Test22 studies name both
- Continuous Performance Test and Go/No-Go Task16 studies name both
- Digit Span Test and Stroop Color-Word Test14 studies name both
- Stroop Color-Word Test and Trail Making Test12 studies name both
- Card Sorting Test (Berg) and Stroop Color-Word Test11 studies name both
- Go/No-Go Task and Stop-Signal Task11 studies name both
- Continuous Performance Test and N-Back Task9 studies name both
- Digit Span Test and Go/No-Go Task9 studies name both
- Digit Span Test and Trail Making Test9 studies name both
Studies by start year
A test as a primary outcomeOnly in secondary or other outcomes
Show as a table
| Start year | Studies | A test as a primary outcome |
|---|---|---|
| 2000 | 2 | 1 |
| 2001 | 0 | 0 |
| 2002 | 0 | 0 |
| 2003 | 1 | 0 |
| 2004 | 1 | 1 |
| 2005 | 7 | 5 |
| 2006 | 3 | 1 |
| 2007 | 5 | 2 |
| 2008 | 8 | 2 |
| 2009 | 14 | 8 |
| 2010 | 9 | 2 |
| 2011 | 11 | 4 |
| 2012 | 11 | 5 |
| 2013 | 14 | 8 |
| 2014 | 22 | 12 |
| 2015 | 15 | 9 |
| 2016 | 17 | 7 |
| 2017 | 18 | 8 |
| 2018 | 19 | 11 |
| 2019 | 22 | 10 |
| 2020 | 13 | 8 |
| 2021 | 19 | 14 |
| 2022 | 25 | 15 |
| 2023 | 27 | 16 |
| 2024 | 27 | 13 |
| 2025 | 27 | 18 |
| 2026 | 18 | 4 |
Phases and sponsors
By phase
- Early phase 19 studies, 5 as a primary outcome
- Phase 110 studies, 7 as a primary outcome
- Phase 1/25 studies, 0 as a primary outcome
- Phase 226 studies, 14 as a primary outcome
- Phase 2/34 studies, 2 as a primary outcome
- Phase 318 studies, 5 as a primary outcome
- Phase 438 studies, 21 as a primary outcome
- Not applicable209 studies, 111 as a primary outcome
- Observational38 studies, 20 as a primary outcome
Sponsors and study types
Lead sponsor: industry 50, NIH 2, universities, hospitals and others 305. Interventional 319, observational 38.
Status, results, interventions and countries
Status
- Recruiting50 studies, 26 as a primary outcome
- Not yet recruiting11 studies, 2 as a primary outcome
- Active, not recruiting10 studies, 5 as a primary outcome
- Completed208 studies, 109 as a primary outcome
- Stopped early19 studies, 13 as a primary outcome
- Status unknown59 studies, 30 as a primary outcome
What they test
- Behavioral102 studies, 45 as a primary outcome
- Drug111 studies, 57 as a primary outcome
- Device58 studies, 33 as a primary outcome
- Dietary supplement24 studies, 12 as a primary outcome
- Procedure6 studies, 3 as a primary outcome
- Diagnostic test7 studies, 5 as a primary outcome
- Biological2 studies, 1 as a primary outcome
- Combination product1 studies, 1 as a primary outcome
- Other85 studies, 52 as a primary outcome
- None given16 studies, 7 as a primary outcome
Intervention types as registered. A study can list several; observational studies often list none.
Where their sites are
- United States132 studies, 81 as a primary outcome
- Taiwan22 studies, 8 as a primary outcome
- France17 studies, 6 as a primary outcome
- United Kingdom16 studies, 5 as a primary outcome
- China14 studies, 7 as a primary outcome
- Israel14 studies, 4 as a primary outcome
- Netherlands14 studies, 5 as a primary outcome
- Germany13 studies, 4 as a primary outcome
- Hong Kong12 studies, 7 as a primary outcome
- Spain12 studies, 3 as a primary outcome
- Brazil11 studies, 3 as a primary outcome
- Canada11 studies, 6 as a primary outcome
36 countries in all. A study with sites in several counts in each; 20 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 ADHD studies: 99 of 208, 48%
Every completed study with a cognitive outcome: 3,626 of 7,953, 46%
| Results | Completed ADHD studies | Every completed study |
|---|---|---|
| Results on ClinicalTrials.gov and a paper | 25, 12% | 776, 10% |
| Results on ClinicalTrials.gov only | 32, 15% | 1,139, 14% |
| A results paper only | 42, 20% | 1,711, 22% |
| Neither | 109, 52% | 4,327, 54% |
How many participants they enroll
- Phase 122 median, 17 to 71
- Phase 243 median, 21 to 84
- Phase 3114 median, 40 to 283
- Phase 478 median, 36 to 153
- Not applicable60 median, 32 to 101
- Observational104 median, 60 to 292
Show as a table
| Phase | Studies with a size | Median | Middle half |
|---|---|---|---|
| Phase 1 | 10 | 22 | 17 to 71 |
| Phase 2 | 26 | 43 | 21 to 84 |
| Phase 3 | 17 | 114 | 40 to 283 |
| Phase 4 | 37 | 78 | 36 to 153 |
| Not applicable | 207 | 60 | 32 to 101 |
| Observational | 38 | 104 | 60 to 292 |
When the cognitive outcome is measured
Latest time point of each outcome
- Within a day97 outcomes, 52 as a primary outcome
- Up to 4 weeks165 outcomes, 72 as a primary outcome
- 1 to 3 months239 outcomes, 99 as a primary outcome
- 3 to 6 months71 outcomes, 40 as a primary outcome
- 6 to 12 months67 outcomes, 19 as a primary outcome
- 1 to 2 years12 outcomes, 3 as a primary outcome
- Over 2 years9 outcomes, 3 as a primary outcome
- No duration given54 outcomes, 32 as a primary outcome
A test as a primary outcomeOnly in secondary or other outcomes
660 of the 714 outcome measures give a duration. A single visit counts as within a day.
Median time to the primary outcome, by test
| Test | Primary outcomes | Median |
|---|---|---|
| Continuous Performance Test | 51 | 8 weeks |
| Go/No-Go Task | 28 | 8 weeks |
| Digit Span Test | 23 | 12 weeks |
| Stop-Signal Task | 20 | 4 weeks |
| N-Back Task | 19 | 5 weeks |
| Stroop Color-Word Test | 18 | 11 weeks |
| Eriksen Flanker Task | 11 | 6 weeks |
Explore the ADHD studies
353 studies match. 185 name a library test in a primary outcome. Median size 63 participants. Median time to the primary outcome: 8 weeks.
Loading 353 studies; the filters turn on when they arrive.
2026 is partly planned starts. Not shown: 1 that started before 2000 and 1 planned to start after 2026.
Show as a table
| Start year | Studies | As a primary outcome |
|---|---|---|
| 2000 | 2 | 1 |
| 2001 | 0 | 0 |
| 2002 | 0 | 0 |
| 2003 | 1 | 0 |
| 2004 | 1 | 1 |
| 2005 | 7 | 5 |
| 2006 | 3 | 1 |
| 2007 | 5 | 2 |
| 2008 | 7 | 2 |
| 2009 | 14 | 8 |
| 2010 | 9 | 2 |
| 2011 | 11 | 4 |
| 2012 | 10 | 5 |
| 2013 | 14 | 8 |
| 2014 | 22 | 12 |
| 2015 | 15 | 9 |
| 2016 | 17 | 7 |
| 2017 | 18 | 8 |
| 2018 | 19 | 11 |
| 2019 | 22 | 10 |
| 2020 | 13 | 8 |
| 2021 | 19 | 14 |
| 2022 | 24 | 15 |
| 2023 | 26 | 16 |
| 2024 | 27 | 13 |
| 2025 | 27 | 18 |
| 2026 | 18 | 4 |
Library tests named most
Largest condition groups
Phases
Participants
Lead sponsor: industry 49, NIH 2, other 302. Interventional 316, observational 37.
As a primary outcomeSecondary or other outcome
The studies, newest registration first
Each number opens the study's record on ClinicalTrials.gov.
| Study | Start | Phase | Conditions | Participants | Lead sponsor | Status | Library tests named, with the latest time point |
|---|---|---|---|---|---|---|---|
| NCT07900451 | Start2026 | PhaseObservational | ConditionsADHD | Participants90 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07900048 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants100 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07863362 | Start2025 | PhaseNot applicable | ConditionsADHD | Participants30 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07793045 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants40 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07777328 | Start2025 | PhaseNot applicable | ConditionsADHD | Participants150 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07767617 | Start2026 | PhaseNot applicable | ConditionsADHD, Sleep and sleep disorders | Participants150 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07716072 | Start2026 | PhaseNot applicable | ConditionsADHD, Autism | Participants120 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07684417 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants50 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07675538 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants30 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07652788 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants40 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07650643 | Start2026 | PhasePhase 4 | ConditionsADHD | Participants220 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07647900 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants60 | Lead sponsorOther | StatusActive, not recruiting | Library tests named
|
| NCT07633275 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants38 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07595783 | Start2024 | PhaseNot applicable | ConditionsADHD | Participants40 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07565402 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants60 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07541820 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants20 | Lead sponsorOther | StatusActive, not recruiting | Library tests named
|
| NCT07521449 | Start2023 | PhaseNot applicable | ConditionsADHD | Participants45 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07499427 | Start2025 | PhaseNot applicable | ConditionsADHD | Participants130 | Lead sponsorOther | StatusStopped early | Library tests named
|
| NCT07478458 | Start2025 | PhaseNot applicable | ConditionsADHD | Participants120 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07477431 | Start2025 | PhasePhase 2 | ConditionsDementia and Alzheimer's, ADHD | Participants40 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07442058 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants35 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07437833 | Start2026 | PhaseNot applicable | ConditionsDepression and bipolar disorder, ADHD | Participants1 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07426302 | Start2023 | PhaseNot applicable | ConditionsADHD, Autism | Participants50 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07426289 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants50 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT07419659 | Start2026 | PhaseNot applicable | ConditionsADHD | Participants80 | Lead sponsorOther | StatusRecruiting | Library tests named
|
Questions, answered from the data
Which cognitive test do ADHD trials use most?
The Continuous Performance Test: 123 of the 357 registered studies name it in an outcome measure, 34%. Next come the Go/No-Go Task (65) and the Stroop Color-Word Test (61).
Which cognitive test do ADHD trials use most as a primary outcome?
The Continuous Performance Test, named in a primary outcome by 56 studies. 185 of the 357 studies, 52%, name a cognitive test in a primary outcome.
How many participants does a phase 2 ADHD trial enroll?
Half of the phase 2 ADHD studies enroll 43 participants or fewer, and the middle half enroll 21 to 84. 26 of them give a size.
How long after the start do ADHD trials measure a cognitive outcome?
Half of the primary outcomes that name a library test are measured within 8 weeks of the start, and the middle half from 1 week to 13 weeks. 288 primary outcomes give a duration.
Which cognitive tests do ADHD trials use together?
The AX Continuous Performance Test with the Continuous Performance Test most often: 36 studies name both. Next, the Continuous Performance Test with the Digit Span Test (22).
How many completed ADHD trials have reported results?
99 of the 208 completed ADHD studies, 48%, have reported results: 57 posted them on ClinicalTrials.gov, 67 have a results paper linked to the registry record, and 25 did both. The other 109 show neither. Of all completed studies with a cognitive outcome, 46% have reported results.
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.
Plan the cognitive outcomes of a ADHD trial
Choose tests with a record in registered trials, and run them in a browser at every site, on the same version each visit.