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CAM Basics
About Clinical Trials and Complementary and Alternative Medicine

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Clinical trials are an important part of the medical research process. Through clinical trials, scientific discoveries can lead to better ways to prevent, detect, and treat diseases and medical conditions. This fact sheet will provide you with an introduction to clinical trials and to trials of complementary and alternative medicine (CAM).


Key Points


What is CAM?

CAM is a group of diverse medical and health care systems, practices, and products that are not presently considered to be part of conventional medicine. Complementary medicine is used together with conventional medicine, and alternative medicine is used in place of conventional medicine. Conventional medicine is medicine as practiced by holders of M.D. (medical doctor) or D.O. (doctor of osteopathy) degrees and by their allied health professionals, such as physical therapists, psychologists, and registered nurses. Some health care providers practice both CAM and conventional medicine.

The list of practices that are considered CAM changes continually, as those therapies that are proven to be safe and effective become adopted into conventional health care and as new approaches to health care emerge.


What is NCCAM's role in the field of CAM?

The National Center for Complementary and Alternative Medicine (NCCAM) is the Federal Government's lead agency for scientific research on CAM. NCCAM's mission is to explore complementary and alternative healing practices in the context of rigorous science, train CAM researchers, and disseminate authoritative information to the public and professionals.


What is a clinical trial?

A clinical trial is a research study in which a treatment or therapy is tested in people to see whether it is safe and effective. The information learned from clinical trials helps to improve health care and to keep people healthier. Researchers also conduct clinical trials to find out which treatments are more effective than others. The results from trials can also contribute to our understanding of diseases and conditions--for example, how a disease progresses or how it affects different systems in the body.

Clinical trials are also called medical research, research studies, or clinical studies. Each trial follows a protocol--a written, detailed plan that explains why there is a need for the study, what it is intended to do, and how it will be conducted. The protocol is written by the trial's principal investigator (the person who is in charge of the trial).


What are the major types of clinical trials?

Clinical trials are used to study many aspects of medical care:

Clinical trials have sometimes been thought of as a last resort for those who have a disease and have tried all other treatment options. This is not true. There are trials for healthy people (for example, to study disease prevention) and trials for all different types and stages of diseases.


What are the different phases of a clinical trial?

Because the therapy will be tested in people, before a clinical trial can start, there needs to be some evidence that it is likely to work. This evidence can come either from previous research studies in animals or from reported information on its use by people.

Clinical trials take place in phases. In each phase, different research questions are answered. The following are types of questions that each phase helps to answer:


What are some common elements of clinical trials?

Trials can be randomized. Each participant in a randomized trial is assigned by chance (through a computer or a table of random numbers) to one of two groups:

Each participant has an equal chance of being assigned to either group. In some complex trials, there are more than two groups. Randomization is used in all phase III studies and in some phase II studies. It gives the best chance of knowing that the study results are caused by the treatment and not some other factor, such as people's choices or beliefs.

Trials can be double-blind. This means that neither the researchers nor the participants know who has been assigned to which group. Blinding is another way to help minimize the chance of bias influencing the trial results. The information is kept on file at a central office, so if there is an urgent need for the research team to find out who was assigned the active treatment, they can.

Researchers design clinical trials to have one or more endpoints. An endpoint is a measure that determines whether the treatment under study has an effect. An example of an endpoint is whether a person's tumor shrinks after receiving chemotherapy.


What is a placebo?

A placebo is designed to resemble as much as possible the treatment being studied in a clinical trial, except that the placebo is inactive. An example of a placebo is a pill containing sugar instead of the drug being studied. By giving one group of participants a placebo and the other group the active treatment, the researchers can compare how the two groups respond and get a truer picture of the active treatment's effects.

Another type of placebo is called a "sham" procedure. When the treatment under study is a procedure (not a drug or other substance), a sham procedure may be designed that resembles the active treatment but does not have any active treatment qualities. For example, in a clinical trial of acupuncture, the sham procedure might consist of placing acupuncture needles in areas of the body that are not expected (from previous knowledge) to have any therapeutic response.

In recent years, the definition of placebo has been expanded to include other things that could have an effect on the results of health care. Examples include how a patient and a health care provider interact, how a patient feels about receiving the care, and what he or she expects to happen from the care. Therefore, when a treatment is compared to a placebo in clinical trials, the patients should differ only in whether they receive treatment, and not in other aspects.

Not all clinical trials compare an active treatment to a placebo. No patient is denied treatment in a clinical trial if there is a standard therapy available that could improve the comfort and survival of the patient.


Who can participate in a clinical trial?

Clinical trials include people of various ages and ethnic groups and both genders as much as possible, so that the results can apply to the general population. Each clinical trial, however, is unique in its eligibility criteria (rules for who can and cannot participate). Examples of criteria include sex, age, type of disease, severity of disease, and history of prior treatment. If a disease is being studied in a trial, participants must have a similar degree of illness, so that there is a good chance they will respond in similar ways to the treatment being studied.


Are there protections for people who participate in clinical trials?

Yes, the Federal Government requires many protections for people who participate in federally funded clinical trials.

Before a clinical trial can start, the written protocol must be approved and monitored by an Institutional Review Board (IRB). An IRB is an independent group of health care providers, other experts, and lay people from the community who make sure that the study is set up and run safely and fairly. IRBs review protocols and the consent documents that people must sign in order to participate in a clinical trial.

Participants are also protected by a process called informed consent. If you are considering taking part in a clinical trial, during this process you will meet with a member of the research team. He or she will provide you with key facts about the study, such as:

You have a right to have all your questions answered. If you do not understand an answer you receive, ask again. It can be helpful to make a list of questions and concerns before you talk to the study team.

The staff will also give you a consent form, an agreement that you will sign if you decide to join the trial. Consent forms can be long, and they contain a lot of information. It is a good idea to take the consent form home, so that you can think about it and review it with family members or friends. If you have an interest in joining a study, it is also very helpful to discuss it with your health care practitioner and others whose advice you trust.

Participating in a clinical trial is completely voluntary. You can leave the trial at any time, for any reason--even after you have signed the consent form.


What happens once a clinical trial starts?

What happens depends on the type of trial and the study protocol. However, some activities are similar for all clinical trials.

The research team will check the participants' health at the beginning of the trial, give specific instructions for participating, and monitor their health carefully during the trial. Participants may be required to do some things between appointments, such as take medication according to a schedule or make a phone call to report their experiences.

Clinical trials take place in a variety of settings, depending on the type of trial and what is being studied. For example, participants in a trial of an herb might follow the protocol at home, while a trial that involves specialized equipment (such as acupuncture) might be carried out in a clinic or other health care setting. Still other trials may require participants to be in a hospital, clinic, or research center while the therapy is given.


What happens after a clinical trial ends?

The researchers carefully analyze the data from the trial. Then they consider what their findings mean and whether there should be further testing. If a trial has been completed and the results have medical importance, they usually report the results first in a peer-reviewed medical journal ("peer reviewed" means that each report is reviewed before publication by a group of experts in the same field). A new treatment that has been found to be safe and effective in a carefully conducted clinical trial may become the new standard practice.

If you are a trial participant, the research team will inform you about the study results soon after the study is completed and all its data are analyzed. Ask the study team when they expect to be able to let you know the results.


What are the possible benefits of being in a clinical trial?


What are the possible risks to being in a clinical trial?

There are possible risks to being in a clinical trial, as there are with any form of treatment and with illness itself. In a clinical trial:


Are clinical trials being done of CAM?

Yes, clinical trials on CAM are taking place throughout the United States and the world.

While many CAM treatments have already been in use for a long time (sometimes for centuries), there is not the kind of scientific knowledge available about them that has been gained from studies of conventional medicine. Many people are already using CAM, and without this scientific knowledge, they may be at risk-for example, for serious effects from taking the wrong dose, using the treatment in the wrong way, or using it with another treatment with which it interacts.

Researchers, including many supported by NCCAM, are studying CAM treatments in well-designed clinical trials to find answers to such questions as:

NCCAM is funding studies on a variety of CAM treatments. A few examples include acupuncture; herbs, such as Ginkgo biloba and saw palmetto; dietary supplements, such as glucosamine and chondroitin; and massage. Examples of diseases and conditions for which these CAM therapies are being studied include arthritis, neurological disorders, cardiovascular disease, and cancer. Some of these studies involve partnerships with other institutes at the National Institutes of Health (NIH). Institutions outside the Federal Government are conducting studies as well.


How do I find out more about CAM clinical trials?

The NCCAM Web site contains a listing of NCCAM-funded clinical trials. is a database of thousands of clinical studies being sponsored by NIH, other Federal agencies, and the pharmaceutical industry. You can also find out more by contacting the NCCAM Clearinghouse. See "For More Information" below for these and other resources.


For More Information

NCCAM Clearinghouse

The NCCAM Clearinghouse provides information on CAM and NCCAM, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

Toll-free in the U.S.: 1-888-644-6226
TTY (for deaf and hard-of-hearing callers): 1-866-464-3615
Web site:

National Institutes of Health (NIH)

NIH's mission is to uncover new knowledge that will lead to better health for everyone. Comprising 27 separate components, mainly institutes and centers, NIH works toward that mission by conducting and supporting research, training researchers, and fostering communication of medical information. Descriptions of each of the institutes and centers, along with their research priorities and links to their Web sites, can be accessed from the main NIH Web site at:

Telephone: 301-496-4000
Web site:
E-mail: is a database of information on federally and privately supported clinical trials (research studies in people) for a wide range of diseases and conditions. It is sponsored by NIH and the U.S. Food and Drug Administration.

Web site:


A service of the National Library of Medicine (NLM), PubMed contains publication information and (in most cases) brief summaries of articles from scientific and medical journals. CAM on PubMed, developed jointly by NCCAM and NLM, is a subset of the PubMed system and focuses on the topic of CAM.

Web site:
Web site:

CRISP (Computer Retrieval of Information on Scientific Projects)

CRISP is a database of information on federally funded scientific and medical research projects being conducted at research institutions.

Web site:


This publication is not copyrighted and is in the public domain. Duplication is encouraged.

NCCAM has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your primary health care provider. We encourage you to discuss any decisions about treatment or care with your health care provider. The mention of any product, service, or therapy is not an endorsement by NCCAM.

NCCAM Publication No. D338
Updated December 2006


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