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Add Health is the National Longitudinal Study of Adolescent to Adult Health, a longitudinal study that has followed a cohort first surveyed as students in grades 7-12 in 1994-1995 into mid-adult life. It is run from the Carolina Population Center at the University of North Carolina at Chapel Hill. This page is for researchers deciding whether the data fit their question and which access route applies. It was checked against the study’s own pages on 2026-11-07.
What Add Health is
Add Health is a longitudinal cohort study: the same people are surveyed repeatedly over decades rather than different people at each time point (see longitudinal study design and cohort studies). The project is housed at the Carolina Population Center, UNC Chapel Hill, according to the Add Health About page. The name is often shortened to “Add Health”, a phrase that has other unrelated uses, so the full study name is the reliable search term.
Who runs it and what it covers
Funding for Wave VI came primarily from the National Institute on Aging (NIA). Earlier waves were funded primarily by the National Institute of Child Health and Human Development (NICHD), with co-funding from 23 other federal agencies and foundations, per the About page. Robert A. Hummer is listed as the current director on the study’s acknowledgement page.
Waves and sample sizes
| Wave | Years | Participants reported by Add Health |
|---|---|---|
| I | 1994-1995 | 90,118 students completed in-school questionnaires; 20,745 were sampled for in-home interviews (grades 7-12) |
| II | 1996 | Nearly 15,000 interviewed |
| III | 2001-2002 | 15,170 |
| IV | 2008 | 15,701 |
| V | 2016-2018 | Sample size not given on the About page |
| VI | 2022-2025 | 11,979 completed the survey; 6,073 completed a home exam; ages 39-51, mean age 44 |
Source: Add Health, About, read 2026-11-07.
How to get the data: choosing an access route
Add Health offers more than one access tier, and the right one depends on who you are and what you plan to do. The study’s Data page describes these routes and refers to a Data Decision Chart.
Public-use data
Public-use files contain all of the survey data but only a subset of the sample; for Waves I-VI the subset sizes range from 3,937 to 6,504 participants. Per the Data page, this tier is for people who are not merging Add Health with other data and who do not hold both a terminal degree and a faculty or research appointment.
Restricted-use data
Restricted-use data cover all participants. They are available to certified researchers who commit to maintaining limited access, and are intended for researchers with a terminal degree and a faculty or research appointment. Contracts are applied for and renewed online through the Add Health Contracts Management System (CMS), reached from the Data Portal. There are two contract types: Secure Research Workspace (SRW) and Home Institution. Wave VI files are available only through the UNC Secure Research Workspace and the Home Institution contract.
Merging with other datasets
To link Add Health to other datasets using unique identifiers, the Data page directs researchers to apply for an ancillary study rather than a restricted-use contract.
Citing and acknowledging Add Health
The data-use contract requires an acknowledgement in any written report or publication. Waves I-V were funded by grant P01 HD31921 (NICHD) and Wave VI by U01 AG071448, with UNC’s NIA award U01 AG071450. Use the exact wording on the study’s acknowledgement page rather than paraphrasing it.
Strengths and limits
- Strength: long follow-up. The same cohort has been surveyed from adolescence (Wave I) to ages 39-51 (Wave VI), supporting life-course questions.
- Strength: in-school and in-home components. Wave I combines a large in-school questionnaire with a smaller in-home interview sample.
- Limit: fewer completers over time. The reported counts fall from 20,745 in-home Wave I participants to 11,979 Wave VI survey completers, so check the study’s documentation before choosing weights.
- Limit: tiered access. Public-use files contain only a subset of the sample, so analyses needing all participants require a restricted-use contract.
Analyses of existing data like this are covered in secondary data analysis explained. Studies that involve minors raise consent questions; see assent.
Related studies
For another large US youth cohort, see the CASRAI guide to the ABCD Study.
FAQ
What does Add Health stand for?
Add Health is the National Longitudinal Study of Adolescent to Adult Health, run from the Carolina Population Center at UNC Chapel Hill.
Who can use Add Health data?
Public-use data are available in subset form. Full-sample restricted-use data are for certified researchers with a terminal degree and a faculty or research appointment, through a contract in the Contracts Management System.
Can I merge Add Health with another dataset?
Not under a restricted-use contract. The Data page says to apply for an ancillary study.
Where can I get Wave VI data?
Only through the UNC Secure Research Workspace and the Home Institution contract.
Sources
- Add Health: About (read 2026-11-07)
- Add Health: Data (read 2026-11-07)
- Add Health: Acknowledgement (read 2026-11-07)
