Clinical trials data
Trial design benchmark
Describe a planned trial by its condition, phase and intervention type, and see what similar registered trials did: the cognitive tests they named as primary and secondary outcomes, how many participants they enrolled and when they measured the outcome. From the 11,688 studies on ClinicalTrials.gov that name a test in the library.
Studies like yours
11,688 registered studies like this name a library test: any condition, any phase, any intervention.
- Participants per study, median
- 60middle half 31 to 120, from 11,460 studies that give a size
- Primary cognitive outcome measured, median
- 8 weeksmiddle half 1 week to 6 months, from 9,314 primary outcomes that give a duration
Tests they name in a primary outcome
Stroop Color-Word Test7% of the studies, 785
Verbal Learning6% of the studies, 711
Trail Making Test6% of the studies, 709
Verbal Fluency5% of the studies, 640
Digit Span Test5% of the studies, 603
Symbol Coding4% of the studies, 451
N-Back Task3% of the studies, 381
Go/No-Go Task3% of the studies, 309
Continuous Performance Test2% of the studies, 265
Category Fluency2% of the studies, 232
Tests they name in a secondary outcome
Trail Making Test12% of the studies, 1,450
Stroop Color-Word Test9% of the studies, 1,060
Verbal Learning9% of the studies, 1,017
Verbal Fluency9% of the studies, 997
Digit Span Test8% of the studies, 939
Symbol Coding8% of the studies, 908
N-Back Task3% of the studies, 368
Go/No-Go Task3% of the studies, 350
Continuous Performance Test3% of the studies, 343
Category Fluency3% of the studies, 341
The study starts with Stroop Color-Word Test, Verbal Learning, Trail Making Test, Verbal Fluency, Digit Span Test: the tests these studies name most in a primary outcome. You can add or remove tests before it starts.
Median participants by condition and phase
| Condition | Phase 1 | Phase 2 | Phase 3 | Phase 4 | No phase | Observational |
|---|---|---|---|---|---|---|
| Every condition | 30(504) | 60(1,341) | 246(635) | 77(671) | 60(9,682) | 111(2,559) |
| Dementia and Alzheimer's | 30(70) | 90(267) | 543(131) | 101(70) | 60(731) | 280(270) |
| Aging, frailty and exercise | 40(16) | 60(27) | too few | 140(14) | 70(1,084) | 160(216) |
| Depression and bipolar disorder | 30(36) | 69(98) | 111(56) | 60(81) | 71(730) | 140(163) |
| Stroke | 27(13) | 80(75) | 363(56) | 200(38) | 50(775) | 120(222) |
| Substance use and addiction | 31(74) | 50(139) | 81(16) | 44(32) | 70(463) | 93(69) |
| Parkinson's disease | 16(30) | 60(88) | 130(21) | 21(32) | 44(504) | 100(163) |
| Mild cognitive impairment | 28(14) | 79(74) | 206(12) | 86(23) | 64(587) | 180(111) |
| Cancer | 21(19) | 60(110) | 226(69) | 57(11) | 60(346) | 100(151) |
| Sleep and sleep disorders | 34(17) | 61(56) | 158(30) | 48(34) | 60(463) | 100(119) |
| Anxiety, PTSD and OCD | 38(15) | 62(47) | 70(12) | 65(21) | 69(465) | 109(81) |
| Cardiovascular disease | too few | 69(28) | 238(28) | 200(41) | 100(377) | 200(167) |
| Pain and fatigue | 32(17) | 100(55) | 72(29) | 102(25) | 59(393) | 93(115) |
| Healthy volunteers | 30(73) | 64(13) | too few | 44(20) | 60(432) | 121(72) |
| Schizophrenia and psychosis | 31(29) | 57(82) | 142(33) | 60(51) | 60(362) | 100(43) |
| Obesity and diabetes | 41(13) | 57(34) | 306(12) | 100(30) | 61(390) | 163(120) |
| Delirium, surgery and intensive care | too few | 93(22) | 290(24) | 136(61) | 107(268) | 150(217) |
| Multiple sclerosis | 28(14) | 60(57) | 828(62) | 111(23) | 50(291) | 86(121) |
| Brain injury and concussion | 40(13) | 43(29) | 133(12) | 40(13) | 41(288) | 92(61) |
| ADHD | 22(10) | 43(26) | 114(17) | 78(37) | 60(207) | 104(38) |
| Cognitive impairment and decline | too few | 40(15) | too few | 80(19) | 60(214) | 122(72) |
| Hearing loss | too few | 78(11) | too few | too few | 40(169) | 80(47) |
| COVID-19 and long COVID | too few | 88(24) | too few | too few | 60(96) | 194(77) |
| Autism | too few | 46(20) | too few | too few | 60(133) | 126(21) |
| Epilepsy | too few | 32(10) | too few | too few | 46(70) | 120(27) |
| Lung disease | too few | too few | too few | too few | 60(53) | 98(38) |
Every registered study in the group counts here, whichever tests it names, as on the condition pages; the benchmark above reads the studies that name a library test. Enrollment is as registered: actual for a finished study, planned for one still recruiting. “No phase” is the registry's “not applicable”, used for behavioral and device trials.
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.
The benchmark counts a test in a primary outcome when a primary outcome measure of the study names it, and its timing is the latest time point of that outcome. The section's main page holds every study, with filters for test, sponsor, status, country, size and start year.
Plan the cognitive outcomes of your trial
Choose tests with a record in registered trials, and run them in a browser at every site, on the same version each visit.