Clinical trials data
Digit Span Test in ADHD trials: 58 registered studies
Every registered ADHD study on ClinicalTrials.gov that names the Digit Span Test in an outcome measure: how often it is a primary outcome, the tests named with it, how large the studies are and when they measure it.
- Registered ADHD studies name it in an outcome measure
- 58
- Name it in a primary outcome, 41%
- 24 of 58
Tests named in the same studies
- 1
Continuous Performance Test22 studies, 10 as a primary outcome
- 2
Stroop Color-Word Test14 studies, 5 as a primary outcome
- 3
Go/No-Go Task9 studies, 5 as a primary outcome
- 4
Trail Making Test9 studies, 2 as a primary outcome
- 5
Letter-Number Sequencing Task8 studies, 3 as a primary outcome
- 6
Symbol Scan Task8 studies, 2 as a primary outcome
- 7
Matrix Reasoning7 studies, 3 as a primary outcome
- 8
Stop-Signal Task6 studies, 2 as a primary outcome
- 9
Card Sorting Test (Berg)6 studies, 1 as a primary outcome
- 10
AX Continuous Performance Test6 studies, 0 as a primary outcome
A test as a primary outcomeOnly in secondary or other outcomes
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 | 0 | 0 |
| 2001 | 0 | 0 |
| 2002 | 0 | 0 |
| 2003 | 0 | 0 |
| 2004 | 1 | 1 |
| 2005 | 1 | 0 |
| 2006 | 0 | 0 |
| 2007 | 2 | 1 |
| 2008 | 3 | 1 |
| 2009 | 5 | 2 |
| 2010 | 2 | 1 |
| 2011 | 2 | 1 |
| 2012 | 2 | 1 |
| 2013 | 1 | 1 |
| 2014 | 3 | 2 |
| 2015 | 3 | 1 |
| 2016 | 1 | 0 |
| 2017 | 5 | 1 |
| 2018 | 4 | 2 |
| 2019 | 2 | 1 |
| 2020 | 3 | 1 |
| 2021 | 1 | 1 |
| 2022 | 2 | 0 |
| 2023 | 2 | 2 |
| 2024 | 4 | 1 |
| 2025 | 6 | 3 |
| 2026 | 3 | 0 |
Phases and study sizes
By phase
- Phase 11 studies, 1 as a primary outcome
- Phase 26 studies, 2 as a primary outcome
- Phase 2/32 studies, 0 as a primary outcome
- Phase 34 studies, 2 as a primary outcome
- Phase 410 studies, 3 as a primary outcome
- Not applicable32 studies, 14 as a primary outcome
- Observational3 studies, 2 as a primary outcome
Participants per study
- Phase 469 median, 33 to 109
- Not applicable49 median, 30 to 83
Show as a table
| Phase | Studies with a size | Median | Middle half |
|---|---|---|---|
| Phase 4 | 10 | 69 | 33 to 109 |
| Not applicable | 32 | 49 | 30 to 83 |
When ADHD trials measure it
Latest time point of each outcome
- Within a day10 outcomes, 2 as a primary outcome
- Up to 4 weeks14 outcomes, 6 as a primary outcome
- 1 to 3 months21 outcomes, 9 as a primary outcome
- 3 to 6 months7 outcomes, 4 as a primary outcome
- 6 to 12 months4 outcomes, 2 as a primary outcome
- 1 to 2 years1 outcomes, 0 as a primary outcome
- No duration given1 outcomes, 1 as a primary outcome
A test as a primary outcomeOnly in secondary or other outcomes
57 of the 58 outcome measures give a duration. A single visit counts as within a day.
Status, results, interventions and countries
Status
- Recruiting6 studies, 2 as a primary outcome
- Not yet recruiting3 studies, 0 as a primary outcome
- Active, not recruiting1 studies, 1 as a primary outcome
- Completed34 studies, 15 as a primary outcome
- Stopped early2 studies, 1 as a primary outcome
- Status unknown12 studies, 5 as a primary outcome
What they test
- Behavioral18 studies, 5 as a primary outcome
- Drug22 studies, 9 as a primary outcome
- Device8 studies, 4 as a primary outcome
- Procedure1 studies, 1 as a primary outcome
- Diagnostic test1 studies, 1 as a primary outcome
- Combination product1 studies, 0 as a primary outcome
- Other13 studies, 8 as a primary outcome
- None given2 studies, 1 as a primary outcome
Intervention types as registered. A study can list several; observational studies often list none.
Where their sites are
- United States16 studies, 5 as a primary outcome
- Hong Kong5 studies, 2 as a primary outcome
- Canada4 studies, 2 as a primary outcome
- Israel4 studies, 2 as a primary outcome
- Netherlands3 studies, 2 as a primary outcome
- Taiwan3 studies, 1 as a primary outcome
- United Kingdom3 studies, 0 as a primary outcome
- Brazil2 studies, 0 as a primary outcome
- Egypt2 studies, 2 as a primary outcome
- Germany2 studies, 0 as a primary outcome
- Iran2 studies, 2 as a primary outcome
- Puerto Rico2 studies, 0 as a primary outcome
21 countries in all. A study with sites in several counts in each; 6 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 that name the Digit Span Test: 16 of 34, 47%
Every completed study with a cognitive outcome: 3,626 of 7,953, 46%
| Results | Completed ADHD studies that name the Digit Span Test | Every completed study |
|---|---|---|
| Results on ClinicalTrials.gov and a paper | 5, 15% | 776, 10% |
| Results on ClinicalTrials.gov only | 6, 18% | 1,139, 14% |
| A results paper only | 5, 15% | 1,711, 22% |
| Neither | 18, 53% | 4,327, 54% |
The 58 studies
58 studies match. 24 name the Digit Span Test in a primary outcome. Median size 52 participants. Median time to the primary outcome: 12 weeks.
Loading 58 studies; the filters turn on when they arrive.
2026 is partly planned starts.
Show as a table
| Start year | Studies | As a primary outcome |
|---|---|---|
| 2000 | 0 | 0 |
| 2001 | 0 | 0 |
| 2002 | 0 | 0 |
| 2003 | 0 | 0 |
| 2004 | 1 | 1 |
| 2005 | 1 | 0 |
| 2006 | 0 | 0 |
| 2007 | 2 | 1 |
| 2008 | 3 | 1 |
| 2009 | 5 | 2 |
| 2010 | 2 | 1 |
| 2011 | 2 | 1 |
| 2012 | 2 | 1 |
| 2013 | 1 | 1 |
| 2014 | 3 | 2 |
| 2015 | 3 | 1 |
| 2016 | 1 | 0 |
| 2017 | 5 | 1 |
| 2018 | 4 | 2 |
| 2019 | 2 | 1 |
| 2020 | 3 | 1 |
| 2021 | 1 | 1 |
| 2022 | 2 | 0 |
| 2023 | 2 | 2 |
| 2024 | 4 | 1 |
| 2025 | 6 | 3 |
| 2026 | 3 | 0 |
Library tests named most
Conditions
Phases
Participants
Lead sponsor: industry 10, other 48. Interventional 55, observational 3.
As a primary outcomeSecondary or other outcomeThe Digit Span Test
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 |
|---|---|---|---|---|---|---|---|
| NCT07767617 | Start2026 | PhaseNot applicable | ConditionsADHD, Sleep and sleep disorders | Participants150 | Lead sponsorOther | StatusNot yet recruiting | 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
|
| NCT07478458 | Start2025 | PhaseNot applicable | ConditionsADHD | Participants120 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07376863 | Start2024 | PhaseNot applicable | ConditionsADHD | Participants51 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07318935 | Start2024 | PhaseNot applicable | ConditionsADHD | Participants69 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT07242625 | Start2025 | PhaseNot applicable | ConditionsADHD, Autism | Participants48 | Lead sponsorIndustry | StatusRecruiting | Library tests named
|
| NCT07145593 | Start2025 | PhaseNot applicable | ConditionsADHD | Participants60 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT07139210 | Start2025 | PhaseNot applicable | ConditionsADHD | Participants30 | Lead sponsorOther | StatusActive, not recruiting | Library tests named
|
| NCT07050225 | Start2025 | PhaseNot applicable | ConditionsADHD | Participants52 | Lead sponsorOther | StatusNot yet recruiting | Library tests named
|
| NCT06749197 | Start2025 | PhaseNot applicable | ConditionsStroke, Brain injury and concussion, ADHD | Participants30 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT06743763 | Start2024 | PhaseNot applicable | ConditionsADHD | Participants110 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT06682949 | Start2024 | PhaseNot applicable | ConditionsADHD | Participants25 | Lead sponsorOther | StatusRecruiting | Library tests named
|
| NCT06657469 | Start2017 | PhaseNot applicable | ConditionsADHD | Participants80 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT05906485 | Start2023 | PhaseNot applicable | ConditionsADHD | Participants138 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT05831839 | Start2023 | PhaseNot applicable | ConditionsADHD, COVID-19 and long COVID | Participants50 | Lead sponsorOther | StatusStatus unknown | Library tests named
|
| NCT05391698 | Start2022 | PhaseNot applicable | ConditionsADHD | Participants16 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT05302362 | Start2022 | PhaseNot applicable | ConditionsBrain injury and concussion, ADHD | Participants12 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT05162729 | Start2021 | PhaseNot applicable | ConditionsADHD | Participants79 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT04337125 | Start2020 | PhaseNot applicable | ConditionsADHD | Participants160 | Lead sponsorOther | StatusStatus unknown | Library tests named
|
| NCT03963661 | Start2019 | PhaseNot applicable | ConditionsStroke, Brain injury and concussion, ADHD | Participants10 | Lead sponsorOther | StatusStatus unknown | Library tests named
|
| NCT03945175 | Start2020 | PhasePhase 3 | ConditionsADHD | Participants52 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT03935646 | Start2020 | PhasePhase 2 | ConditionsADHD | Participants40 | Lead sponsorOther | StatusStatus unknown | Library tests named
|
| NCT03806946 | Start2019 | PhaseObservational | ConditionsADHD, Epilepsy | Participants100 | Lead sponsorOther | StatusCompleted | Library tests named
|
| NCT03690674 | Start2018 | PhaseNot applicable | ConditionsADHD | Participants35 | Lead sponsorOther | StatusCompleted | Library tests named
|
Questions, answered from the data
How many ADHD trials use the Digit Span Test?
58 registered ADHD studies on ClinicalTrials.gov name it in an outcome measure, 24 of them in a primary outcome: 16% of the condition's 357 studies with a cognitive outcome, against 10% of all of them. It is the 4th most named test in ADHD trials.
Which tests do ADHD trials use with the Digit Span Test?
The Continuous Performance Test (22 studies), the Stroop Color-Word Test (14 studies) and the Go/No-Go Task (9 studies).
When do ADHD trials measure the Digit Span Test?
Half of the primary outcomes that name the Digit Span Test are measured within 12 weeks of the start, and the middle half from 3 weeks to 15 weeks. 23 primary outcomes give a duration.
How many completed ADHD trials that use the Digit Span Test have reported results?
16 of the 34 completed studies that name it, 47%, have reported results: 11 posted them on ClinicalTrials.gov, 10 have a results paper linked to the registry record, and 5 did both. The other 18 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.
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