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Overview of Complementary and Alternative Medicine (CAM)

By Steven Novella, MD, Assistant Professor of Neurology, Yale University School of Medicine

Complementary and alternative medicine (CAM) includes a variety of healing approaches and therapies that are taken from around the world and that historically have not been included in conventional Western medicine. Many aspects of CAM are rooted in ancient, indigenous systems of healing, such as those of China, India, Tibet, Africa, and the Americas.

Many of these treatments and health care practices are popular, and now some are used in hospitals and are reimbursed by insurance companies. Acupuncture and some chiropractic treatments are examples. Because interest in and use of CAM are increasing, more and more medical schools are including information about CAM treatments, such as acupuncture, herbal medicine, chiropractic treatments, and homeopathy.

Different terms are used for CAM, depending on how it is used:

  • Complementary medicine: CAM practices are used with conventional medicine.

  • Alternative medicine: CAM is used alone.

  • Integrative medicine refers to the use of all appropriate therapeutic approaches (conventional and alternative) in a framework that focuses on the whole person and that reaffirms the relationship between doctor and patient.

Although the distinction between conventional medicine and alternative medicine is not always easy to determine, a basic philosophical difference exists. Conventional medicine tends to base its practices on the best scientific evidence available. In contrast, CAM tends to base its practices on philosophy and does not require scientific evidence to justify use of a treatment. Conventional medicine generally defines health as the absence of disease or dysfunction. The main causes of disease and dysfunction are usually considered to be isolated factors, such as bacteria or viruses, biochemical imbalances, and aging, and treatment often involves drugs or surgery. In contrast, alternative medicine practices often define health holistically, that is, as a balance of systems—physical, emotional, and spiritual—involving the whole person. Disharmony among these systems is thought to cause illness. Treatment involves strengthening the body’s own defenses and restoring these balances.

Differences Between Conventional and Alternative Medicine


Conventional Medicine

Alternative Medicine

Definition of health

A condition of physical, mental, and social well-being and the absence of disease and other abnormalities

Optimal balance, resilience, and integrity of the body, mind, and spirit and their interrelationships

Definition of illness

Malfunction of an organ or a physical or biochemical process or undesirable symptoms

Caused by factors such as bacteria or viruses, biochemical imbalances, or aging

Imbalance of body, mind, and spirit

Based on a person's specific symptoms and unique physical, mental, and spiritual make-up

Concept of life force

Internal processes that are based on known physical laws and involve physical and biochemical processes

A nonphysical, scientifically inaccessible life force that unites mind and body, interconnects all living beings, and is the underpinning of health (often called vitalism)

Understanding of consciousness

Results only from physical processes in the brain

May or may not be created in the brain

Can help the body heal

Method of treatment

Any treatment that is supported by scientific evidence, including drugs, surgery, medical devices, physical therapy, exercise, diet, and changes in lifestyle

Support and strengthening of the body's innate ability to heal

Reliance on scientific evidence

Strict reliance on established principles of scientific evidence

Flexible use of scientific evidence, with treatments often based on tradition and/or anecdotal support instead

Acceptance and Use

Many people in Western countries are exploring alternative medicine as part of their medical care. In 2007, about 38.1 million adults in the United States made about 354.2 million visits to alternative medicine practitioners—a decrease of almost 50% since 1997. This number is substantially lower than the number of visits made to all conventional medicine doctors in the same year.

In 2007, about 38% of Americans 18 years of age or older used some form of alternative medicine, including the following:

  • Natural products (not including vitamins and minerals), such as echinacea, ginseng, ginkgo, and garlic supplements: 17.7%

  • Deep breathing exercises: 12.7%

  • Chiropractic: 8.6%

  • Massage: 8.3%

  • Yoga: 6.1%

Use of other CAM therapies is lower:

The conditions for which people are most likely to seek alternative medicine treatments include the following:

  • Musculoskeletal problems (for example, chronic lower back pain, neck pain, or joint pain)

  • Anxiety

  • High blood cholesterol levels

  • Head or chest colds

  • Headaches

  • Sleep problems

Additionally, many people facing life-challenging illnesses, such as cancer, seek alternative therapies when conventional treatment offers little hope, especially at the end of life.

Effectiveness and Safety

In 1992, the Office of Alternative Medicine within the National Institutes of Health (NIH) was formed to research the effectiveness and safety of alternative therapies. In 1999, this office became the National Center for Complementary and Alternative Medicine, and in 2014, it was renamed the National Center for Complementary and Integrative Health (NCCIH).


The effectiveness of alternative therapies is an important consideration.

Many CAM therapies have been studied and found to be ineffective or, at best, inconsistent. Some therapies have been shown to be effective for a few specific conditions. However, these therapies are often also used to treat other conditions and symptoms, even though no scientific evidence supports these uses. Some CAM therapies have not been tested in well-designed studies. However, a lack of evidence from well-designed studies is not proof that a therapy is ineffective.

Many alternative therapies are said to have been practiced for hundreds or thousands of years. They include acupuncture, meditation, yoga, therapeutic diets, massage, and herbal medicine. Having a long history of use is sometimes used as evidence that alternative therapies are effective. However, there are problems with this argument:

  • Being used for a long time is not proof that a therapy is effective. Some therapies that are now known to be ineffective or harmful were used for hundred or thousands of years.

  • For some therapies, there is no evidence that they actually have such a long history.

  • How a therapy was used in the past may differ from how it is used now.

Thus, well-designed studies are still needed to determine whether a therapy is effective.

However, well-designed studies of CAM therapies can be difficult to do. Barriers to doing research on CAM therapies include the following:

  • Lack of interest in CAM among medical researchers

  • Lack of interest in scientific research among advocates of CAM

  • No laws similar to those that govern conventional medicine requiring proof that CAM products or therapies are effective

Applying conventional research methods to study CAM may be difficult for many reasons, including

  • Conventional research design typically requires that the same treatment be given to every person in the study (subject). However, many CAM therapies try to take the unique and particular imbalances of individual people into account. Thus, people with the same medical diagnosis often are given different treatments. For example, people may have acupuncture needles placed in different locations or may be prescribed completely different homeopathic or herbal medicines.

  • Conventional research design compares active treatment (such as a drug or treatment) with a placebo (an intervention that is made to resemble a drug or treatment but does not include an active drug or treatment). For some CAM therapies, such as homeopathy and herbal medicine, designing a placebo is relatively easy. However, designing a placebo for physical treatments such as acupuncture or chiropractic treatment is more difficult (but not impossible). Designing a placebo for meditation is impossible.

  • Separating the effects of a CAM therapy's active component from those of placebo is difficult. For example, CAM therapists typically interact with people in a positive and supportive way that is known to make people feel better, regardless of what other therapies are used. This aspect of CAM can be viewed as a placebo effect.

  • Conventional research design uses the method of double blinding. Double blinding involves preventing research subjects and practitioners from knowing which people were given which treatment. People and practitioners typically expect the active treatment to do better than the placebo. Double blinding reduces the likelihood that this expectation will bias the results in favor of the treatment. However, blinding practitioners may be difficult. For example, a Reiki practitioner would know whether a real energy treatment is being given. In such cases, the effectiveness of the treatment should be evaluated by another practitioner, who does not know which treatment was used.

  • CAM therapies and diagnoses may not be standardized. For example, different practitioners use different systems of acupuncture, and the contents and effects of medicinal herb preparations vary widely.

However, despite these challenges, many well-designed studies of CAM therapies (such as acupuncture and homeopathy) have been done. For example, one study of acupuncture used a well-designed placebo, which made double blinding possible. It used an opaque sheath that was pressed against the person's skin at an acupuncture point. Some sheaths contained a needle that penetrated the skin (active treatment), and some did not (placebo). For CAM therapies to be considered effective, there should be evidence that they are more effective than placebo.

Lack of funding for well-designed CAM studies is often mentioned as a reason that these studies are not done. For example,it has been suggested that pharmaceutical companies, which conduct many drug studies, do not study CAM drugs because they cannot make money from CAM products. However, CAM products are a multibillion dollar business, suggesting that lack of profitability is not a reason pharmaceutical companies do not study these products. On the other hand, because CAM is profitable, CAM companies risk losing money if they do studies that prove that a CAM product or therapy is ineffective.


Safety is another important consideration.

The greatest risk of CAM may be

  • Use of an unproven CAM therapy instead of a proven conventional therapy to treat a life-threatening disorder

Regarding the risk of CAM therapies themselves, some are clearly safe. Examples are using meditation for pain management, acupuncture to treat nausea, yoga to improve balance, or ginger tea to aid digestion. Others may conceivably be harmful. Because medicinal herbs and other dietary supplements (which are used in many alternative therapies) are not regulated as drugs by the Food and Drug Administration (FDA), their manufacturers do not have to prove their safety (see Overview of Medicinal Herbs and Nutraceuticals : Safety and Effectiveness).

Some general risks include the following:

  • Some substances in CAM preparations may interact dangerously with each other or with prescription drugs.

  • Highly purified dietary supplements are readily available in the United States and many countries in Europe, but products produced in other countries may contain dangerous contaminants, toxic ingredients, or other drugs.

  • Harm can be done by alternative therapies that involve manipulation of the body or other nonchemical interventions (for example, manipulation that injures vulnerable parts of the body).

In many cases of alternative medicine, harm has neither been established nor excluded, but in some cases, potential harm has been shown. Sometimes the potential for harm is widely discounted by people who advocate use of the alternative product or therapy.

Did You Know...

  • Perhaps the greatest risk of CAM occurs when a person with a life-threatening disorder is treated with an unproven CAM therapy instead of a proven conventional medicine therapy.

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