The National Institutes of Health (NIH) (/ɛnaɪˈeɪtʃ/; each letter separately) is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the late 1870s, and is now part of the United States Department of Health and Human Services. The majority of NIH facilities are located in Bethesda, Maryland. The NIH conducts its own scientific research through its Intramural Research Program (IRP) and provides major biomedical research funding to non-NIH research facilities through its Extramural Research Program.

As of 2013, the IRP had 1,200 principal investigators and more than 4,000 postdoctoral fellows in basic, translational, and clinical research, being the largest biomedical research institution in the world,^[5] while, as of 2003, the extramural arm provided 28% of biomedical research funding spent annually in the U.S., or about US$26.4 billion.^[6]

The NIH comprises 27 separate institutes and centers of different biomedical disciplines and is responsible for many scientific accomplishments, including the discovery of fluoride to prevent tooth decay, the use of lithium to manage bipolar disorder, and the creation of vaccines against hepatitis, Haemophilus influenzae (HIB), and human papillomavirus (HPV).^[7]

In 2019, the NIH was ranked #2 in the world for biomedical sciences by the Nature Index, which measured the largest contributors to papers published in a subset of leading journals from 2015-2018.^[8][9]

NIH's roots extend back to the Marine Hospital Service in the late 1790s that provided medical relief to sick and disabled men in the U.S. Navy. By 1870, a network of marine hospitals had developed and was placed under the charge of a medical officer within the Bureau of the Treasury Department. In the late 1870s, Congress allocated funds to investigate the causes of epidemics like cholera and yellow fever, and it created the National Board of Health, making medical research an official government initiative.^[11]

In 1887, a laboratory for the study of bacteria, the Hygienic Laboratory, was established at the Marine Hospital in New York.^[12][13] In the early 1900s, Congress began appropriating funds for the Marine Hospital Service. By 1922, this organization changed its name to Public Health Services and established a Special Cancer Investigations laboratory at Harvard Medical School. This marked the beginning of a partnership with universities. In 1930, the Hygienic Laboratory was re-designated as the National Institute of Health by the Ransdell Act, and was given $750,000 to construct two NIH buildings. Over the next few decades, Congress would increase funding tremendously to the NIH, and various institutes and centers within the NIH were created for specific research programs.^[14] In 1944, the Public Health Service Act was approved, and the National Cancer Institute became a division of NIH. In 1948, the name changed from National Institute of Health to National Institutes of Health.

In the 1960s, virologist and cancer researcher Chester M. Southam injected HeLa cancer cells into patients at the Jewish Chronic Disease Hospital.^{[15] []} When three doctors resigned after refusing to inject patients without their consent, the experiment gained considerable media attention.^{[15] []} The NIH was a major source of funding for Southam's research and had required all research involving human subjects to obtain their consent prior to any experimentation.^{[15] []} Upon investigating all of their grantee institutions, the NIH discovered that the majority of them did not protect the rights of human subjects. From then on, the NIH has required all grantee institutions to approve any research proposals involving human experimentation with review boards.^{[15] []}

In 1967, the Division of Regional Medical Programs was created to administer grants for research for heart disease, cancer, and strokes. That same year, the NIH director lobbied the White House for increased federal funding in order to increase research and the speed with which health benefits could be brought to the people. An advisory committee was formed to oversee further development of the NIH and its research programs. By 1971 cancer research was in full force and President Nixon signed the National Cancer Act, initiating a National Cancer Program, President's Cancer Panel, National Cancer Advisory Board, and 15 new research, training, and demonstration centers.^[16]

Funding for the NIH has often been a source of contention in Congress, serving as a proxy for the political currents of the time. In 1992, the NIH encompassed nearly 1 percent of the federal government's operating budget and controlled more than 50 percent of all funding for health research, and 85 percent of all funding for health studies in universities.^[17] While government funding for research in other disciplines has been increasing at a rate similar to inflation since the 1970s, research funding for the NIH nearly tripled through the 1990s and early 2000s, but has remained relatively stagnant since then.^[18]

By the 1990s, the NIH committee focus had shifted to DNA research, and launched the Human Genome Project.^[19]

The NIH Office of the Director is the central office responsible for setting policy for NIH, and for planning, managing and coordinating the programs and activities of all NIH components. The NIH Director plays an active role in shaping the agency's activities and outlook. The Director is responsible for providing leadership to the Institutes and Centers by identifying needs and opportunities, especially in efforts involving multiple Institutes.^[20] Within this Office is the Division of Program Coordination, Planning and Strategic Initiatives with 12 divisions including:

Previous directors:

Intramural research is primarily conducted at the main campus in Bethesda, Maryland and Rockville, Maryland, and the surrounding communities.

The Bayview Campus in Baltimore, Maryland houses the research programs of the National Institute on Aging, National Institute on Drug Abuse, and National Human Genome Research Institute with nearly 1,000 scientists and support staff.^[22] The Frederick National Laboratory in Frederick, MD and the nearby Riverside Research Park, houses many components of the National Cancer Institute, including the Center for Cancer Research, Office of Scientific Operations, Management Operations Support Branch, the division of Cancer Epidemiology and Genetics and the division of Cancer Treatment and Diagnosis.^[23]

The National Institute of Environmental Health Sciences is located in the Research Triangle region of North Carolina.

Other ICs have satellite locations in addition to operations at the main campus. The National Institute of Allergy and Infectious Diseases maintains its Rocky Mountain Labs in Hamilton, Montana,^[24] with an emphasis on BSL3 and BSL4 laboratory work. NIDKK operates the Phoenix Epidemiology and Clinical Research Branch in Phoenix, AZ.

As of 2017, 153 scientists receiving financial support from the NIH have been awarded a Nobel Prize and 195 have been awarded a Lasker Award.^[25]

NIH devotes 10% of its funding to research within its own facilities (intramural research), and gives >80% of its funding in research grants to extramural (outside) researchers.^[2] Of this extramural funding, a certain percentage (2.8% in 2014) must be granted to small businesses under the SBIR/STTR program.^[26] As of 2011, the extramural funding consisted of about 50,000 grants to more than 325,000 researchers at more than 3000 institutions.^[27] By 2018, this rate of granting remained reasonably steady, at 47,000 grants to 2,700 organizations.^[2] In FY 2010, NIH spent US$10.7bn (not including temporary funding from the American Recovery and Reinvestment Act of 2009) on clinical research, US$7.4bn on genetics-related research, US$6.0bn on prevention research, US$5.8bn on cancer, and US$5.7bn on biotechnology.^[28]

In 2008 a Congressional mandate called for investigators funded by the NIH to submit an electronic version of their final manuscripts to the National Library of Medicine's research repository, PubMed Central (PMC), no later than 12 months after the official date of publication.^[29] The NIH Public Access Policy was the first public access mandate for a U.S. public funding agency.^[30]

On February 13, 2012, the National Institutes of Health (NIH) announced a new group of individuals assigned to research pain. This committee is composed of researchers from different organizations and will focus to "coordinate pain research activities across the federal government with the goals of stimulating pain research collaboration… and providing an important avenue for public involvement" ("Members of new," 2012). With a committee such as this research will not be conducted by each individual organization or person but instead a collaborating group which will increase the information available. With this hopefully more pain management will be available including techniques for arthritis sufferers.^[31]

In 2000, the Joint Economic Committee of Congress reported NIH research, which was funded at $16 billion a year in 2000, that some econometric studies had given a rate of return of 25 to 40 percent per year by reducing the economic cost of illness in the US. It found that of the 21 drugs with the highest therapeutic impact on society introduced between 1965 and 1992, public funding was "instrumental" for 15.^[32] As of 2011 NIH-supported research helped to discover 153 new FDA-approved drugs, vaccines, and new indications for drugs in the 40 years prior.^[33] One study found NIH funding aided either directly or indirectly in developing the drugs or drug targets for all of the 210 FDA-approved drugs from 2010 to 2016.^[34] In 2015, Pierre Azoulay et al. estimated $10 million invested in research generated two to three new patents.^[35]

Since its inception, the NIH intramural research program has been a source of many pivotal scientific and medical discoveries. Some of these include:

In September 2006, the NIH Blueprint for Neuroscience Research started a contract for the NIH Toolbox for the Assessment of Neurological and Behavioral Function to develop a set of state-of-the-art measurement tools to enhance collection of data in large cohort studies. Scientists from more than 100 institutions nationwide contributed. In September 2012, the NIH Toolbox was rolled out to the research community. NIH Toolbox assessments are based, where possible, on Item Response Theory and adapted for testing by computer.

To allocate funds, the NIH must first obtain its budget from Congress. This process begins with institute and center (IC) leaders collaborating with scientists to determine the most important and promising research areas within their fields. IC leaders discuss research areas with NIH management who then develops a budget request for continuing projects, new research proposals, and new initiatives from the Director. NIH submits its budget request to the Department of Health and Human Services (HHS), and the HHS considers this request as a portion of its budget. Many adjustments and appeals occur between NIH and HHS before the agency submits NIH's budget request to the Office of Management and Budget (OMB). OMB determines what amounts and research areas are approved for incorporation into the President's final budget. The President then sends NIH's budget request to Congress in February for the next fiscal year's allocations.^[37] The House and Senate Appropriations Subcommittees deliberate and by fall, Congress usually appropriates funding. This process takes approximately 18 months before the NIH can allocate any actual funds.^[38]

Over the last century, the responsibility to allocate funding has shifted from the OD and Advisory Committee to the individual ICs and Congress increasingly set apart funding for particular causes. In the 1970s, Congress began to earmark funds specifically for cancer research, and in the 1980s there was a significant amount allocated for AIDS/HIV research.^[39]

Funding for the NIH has often been a source of contention in Congress, serving as a proxy for the political currents of the time. During the 1980s, President Reagan repeatedly tried to cut funding for research, only to see Congress partly restore funding. The political contention over NIH funding slowed the nation's response to the AIDS epidemic; while AIDS was reported in newspaper articles from 1981, no funding was provided for research on the disease. In 1984 National Cancer Institute scientists found implications that "variants of a human cancer virus called HTLV-III are the primary cause of acquired immunodeficiency syndrome (AIDS)," a new epidemic that gripped the nation.^[40]

In 1992, the NIH encompassed nearly 1 percent of the federal government's operating budget and controlled more than 50 percent of all funding for health research and 85 percent of all funding for health studies in universities.^[17] From 1993 to 2001 the NIH budget doubled. Since then, funding essentially remained flat, and during the decade following the financial crisis, the NIH budget struggled to keep up with inflation.^[41]

In 1999 Congress increased the NIH's budget by $2.3 billion^[39] to $17.2 billion in 2000.^[42] In 2009 Congress again increased the NIH budget to $31 billion in 2010.^[42] In 2017 and 2018, Congress passed laws with bipartisan support that substantially increasing appropriations for NIH, which was 37.3 billion dollars annually in FY2018.^[43][44]

Researchers at universities or other institutions outside of NIH can apply for research project grants (RPGs) from the NIH. There are numerous funding mechanisms for different project types (e.g., basic research, clinical research etc.) and career stages (e.g., early career, postdoc fellowships etc.). The NIH regularly issues "requests for applications" (RFAs), e.g., on specific programmatic priorities or timely medical problems (such as Zika virus research in early 2016). In addition, researchers can apply for "investigator-initiated grants" whose subject is determined by the scientist.

The total number of applicants has increased substantially, from about 60,000 investigators who had applied during the period from 1999 to 2003 to slightly less than 90,000 in who had applied during the period from 2011 to 2015.^[45] Due to this, the "cumulative investigator rate," that is, the likelihood that unique investigators are funded over a 5-year window, has declined from 43% to 31%.^[45]

R01 grants are the most common funding mechanism and include investigator-initiated projects. The roughly 27,000 to 29,000 R01 applications had a funding success of 17-19% during 2012 though 2014. Similarly, the 13,000 to 14,000 R21 applications had a funding success of 13-14% during the same period.^[46] In FY 2016, the total number of grant applications received by the NIH was 54,220, with approximately 19% being awarded funding.^[47] Institutes have varying funding rates. The National Cancer Institute awarded funding to 12% of applicants, while the National Institute for General Medical Science awarded funding to 30% of applicants.^[47]

NIH employs five broad decision criteria in its funding policy. First, ensure the highest quality of scientific research by employing an arduous peer review process. Second, seize opportunities that have the greatest potential to yield new knowledge and that will lead to better prevention and treatment of disease. Third, maintain a diverse research portfolio in order to capitalize on major discoveries in a variety of fields such as cell biology, genetics, physics, engineering, and computer science. Fourth, address public health needs according to the disease burden (e.g., prevalence and mortality). And fifth, construct and support the scientific infrastructure (e.g., well-equipped laboratories and safe research facilities) necessary to conduct research.^[48]

Advisory committee members advise the Institute on policy and procedures affecting the external research programs and provide a second level of review for all grant and cooperative agreement applications considered by the Institute for funding.^[49]

In 2014, it was announced that the NIH is directing scientists to perform their experiments with both female and male animals, or cells derived from females as well as males if they are studying cell cultures, and that the NIH would take the balance of each study design into consideration when awarding grants.^[50] The announcement also stated that this rule would probably not apply when studying sex-specific diseases (for example, ovarian or testicular cancer).^[50]

When a government shutdown occurs, the NIH continues to treat people who are already enrolled in clinical trials, but does not start any new clinical trials and does not admit new patients who are not already enrolled in a clinical trial, except for the most critically ill,^[51][52][53] as determined by the NIH Director.^[54]

One of the goals of the NIH is to "expand the base in medical and associated sciences in order to ensure a continued high return on the public investment in research."^[55] Taxpayer dollars funding NIH are from the taxpayers, making them the primary beneficiaries of advances in research. Thus, the general public is a key stakeholder in the decisions resulting from the NIH funding policy.^[56] However, some in the general public do not feel their interests are being represented, and individuals have formed patient advocacy groups to represent their own interests.^[57]

Important stakeholders of the NIH funding policy include researchers and scientists. Extramural researchers differ from intramural researchers in that they are not employed by the NIH but may apply for funding. Throughout the history of the NIH, the amount of funding received has increased, but the proportion to each IC remains relatively constant. The individual ICs then decide who will receive the grant money and how much will be allotted.

Policy changes on who receives funding significantly affects researchers. For example, the NIH has recently attempted to approve more first-time NIH R01 applicants, or the research grant applications of young scientists. To encourage the participation of young scientists, the application process has been shortened and made easier.^[58] In addition, first-time applicants are being offered more funding for their research grants than those who have received grants in the past.^[59]

In 2011 and 2012, the Department of Health and Human Services Office of Inspector General published a series of audit reports revealing that throughout the fiscal years 2000–2010, institutes under the aegis of the NIH did not comply with the time and amount requirements specified in appropriations statutes, in awarding federal contracts to commercial partners, committing the federal government to tens of millions of dollars of expenditure ahead of appropriation of funds from Congress.^[60]

The NIH is composed of 27 separate institutes and centers (ICs) that conduct and coordinate research across different disciplines of biomedical science. These are:

In addition, the National Center for Research Resources operated from April 13, 1962 to December 23, 2011.