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Overview of Complementary and Alternative Medicine

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

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Patient Education

Complementary and alternative medicine (CAM) refers to an eclectic mixture of healing approaches and therapies that historically have not been included in conventional, mainstream Western medicine.

CAM is often thought of as medicine that is not based on the principles of mainstream Western medicine. However, this characterization is not strictly accurate.

Probably the key differences between CAM and mainstream medicine concern

  • Scientific validation (if scientifically validated, practices are considered mainstream)

  • The basis for their practices (a related issue)

Most CAM therapies have not been scientifically validated, and this standard has been used to distinguish the 2 types of medicine. However, use of some nutritional supplements, which are often included in CAM, has been scientifically validated and can be considered mainstream. Some CAM therapies are now offered in hospitals and are sometimes reimbursed by insurance companies, further blurring the boundaries. Some traditional medical schools, including 45 North American medical schools in the Consortium of Academic Health Centers for Integrative Medicine, provide education about CAM and integrative medicine.

Mainstream medicine intends to base its practices only on the best scientific evidence available. In contrast, CAM tends to base its practices on philosophy—sometimes conflicting and even mutually exclusive philosophies—and does not rely on strict evidence-based standards.

As many as 38% of adults and 12% of children have used CAM at some point, depending on how broadly CAM is defined. According to the most recent National Health Interview survey (2007), the CAM therapies most commonly used by adults in the US during the past 12 mo included

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

  • Deep breathing exercises (12.7%)

  • Chiropractic or osteopathic manipulation (8.6%)

  • Massage (8.3%)

  • Yoga (6.1%)

Use of other CAM therapies and approaches remains low: homeopathy, naturopathy, and energy healing. A 2006 survey reported that in the US, 53% of adults used at least one dietary supplement.

Because patients worry about being criticized, they do not always volunteer information about their use of CAM to physicians. Therefore, it is very important for physicians to specifically ask their patients about CAM use (including use of medicinal herbs and nutritional supplements) in an open, nonjudgmental way. Learning about patients’ use of CAM can do the following:

  • Strengthen rapport and build trust

  • Provide an opportunity to discuss evidence for CAM and its plausibility and risks.

  • Sometimes help physicians identify and avoid potentially harmful interactions between drugs and CAM therapies or nutritional supplements

  • Monitor patient progress

  • Help patients determine whether they should use specific certified or licensed CAM practitioners

  • Learn from patients’ experiences with CAM

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

Organ dysfunction, disordered biochemical processes, or undesirable symptoms

Symptom and individual based: Imbalance of body, mind, and spirit

Concept of life force

Life processes that are based on known physical laws and that involve physical and biochemical events

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

Not localized to the brain; can exert healing effects on the body

Method of treatment

Any evidence-based intervention, including drugs, surgery, radiation therapy, electrical treatments, medical devices, physical therapy, exercise, and nutritional and lifestyle interventions

Support and strengthening of patients’ inherent capacity for self-healing

Reliance on scientific evidence

Strict reliance on established principles of scientific evidence

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


In 1992, the Office of Alternative Medicine in the National Institutes of Health (NIH) was formed to study the efficacy and safety of alternative therapies. In 1998, this office became the National Center for Complementary and Alternative Medicine (NCCAM), and in 2015, it became the National Center for Complementary and Integrative Health (NCCIH). Other NIH offices (eg, National Cancer Institute) also fund some CAM research. A 2009 review of research funded by the NCCAM found that in their first 10 yr, NCCAM spent 2.5 billion dollars on studies of CAM therapies without providing clear evidence of efficacy for any CAM therapy.

There are 3 types of support for CAM therapies:

  • Efficacy on clinical outcomes as shown in controlled clinical trials (considered the strongest evidence for clinical uses)

  • Evidence of established physiologic mechanisms of action (eg, modification of γ-aminobutyric acid [GABA] activity in the brain by valerian), although evidence of a validated physiologic mechanism of action does not necessarily indicate efficacy on clinical outcomes

  • Use over periods of time ranging from decades to centuries (considered an anecdotal and unreliable form of evidence)

A substantial amount of information about CAM is available in peer-reviewed publications, evidence-based reviews, expert panel consensus documents, and authoritative textbooks; much of it has been published in languages other than English (eg, German, Chinese). Many CAM therapies have been studied and found to be ineffective, or at best, the studies had conflicting and inconsistent results. Some CAM therapies have not been tested in definitive clinical trials. Factors that limit such research include the following:

  • Industry has no financial incentive to fund research.

  • Often, CAM is not practiced in a culture of evidence-based medicine.

  • Manufacturers of CAM products do not have to prove disease-specific efficacy.

The FDA, under the Dietary Supplement Health and Education Act of 1994, allows marketing of dietary supplements and use of CAM devices but significantly restricts efficacy claims. Generally, manufacturers of dietary supplements can claim, without having to provide evidence for safety or efficacy to the FDA, benefit to the body’s structure or function (eg, improves cardiovascular health) but cannot claim benefit for treating disease (eg, treats hypertension).


Designing studies of CAM therapies poses challenges beyond those faced by researchers of conventional therapies:

  • Therapies may not be standardized. For example, there are different systems of acupuncture, and the contents and biologic activity of extracts made from the same plant species vary widely (chemical identification and standardization of active ingredients is not considered part of CAM).

  • Diagnoses may not be standardized; use of many CAM therapies (eg, traditional herbal medicine, homeopathy, acupuncture) is based on the patient’s unique characteristics rather than on a specific disease or disorder.

  • Double- or single-blinding is often difficult or impossible. For example, patients cannot be blinded as to whether they are practicing meditation. Reiki practitioners cannot be blinded as to whether or not they are using energy healing.

  • Outcomes are difficult to standardize because they are often specific to the individual rather than objective and uniform (as mean arterial pressure, Hb A1c level, and mortality are).

  • Placebos may be difficult to devise because identifying the effective component of a CAM therapy may be difficult. For example, in massage, the effective component could be touching, the specific area of the body massaged, the particular massage technique used, or time spent with the patient.

From a conventional research perspective, use of a placebo control is particularly important when subjective outcomes (eg, pain, nausea, indigestion) are used and when disorders that are intermittent, self-limited, or both (eg, headaches) are being studied; such end points and disorders are often the targets of CAM therapies. However, CAM systems interpret placebo effects as nonspecific healing effects that arise out of the therapeutic interaction and are inseparable from specific treatments. In practice, alternative therapies are intended to enhance the quality of the healing environment and therapeutic relationship and thus optimize the patient’s capacity for self-healing (placebo response) as well as treatment-specific effects, making it hard to separate the effects of the specific treatment from those of a placebo. Thus, studying the effective components of a CAM therapy without undermining the integrity of that therapy in a research setting remains a methodologic challenge.

This interpretation of placebo is controversial. Many studies suggest that placebo effects (eg, regression to the mean) are mostly subjective and statistical and do not represent any meaningful self-healing. Researchers can reasonably isolate specific variables of individual treatments and determine whether those variables add to overall efficacy.

Despite these challenges, many high-quality studies of CAM therapies (eg, acupuncture, homeopathy) have been designed and done. For example, one study1 determined that double-blinding was possible for acupuncture when an opaque sheath that contained a penetrating or nonpenetrating needle was used. Another study2 compared the effects of acupuncture (individualized or standardized) with those of simulated acupuncture using a toothpick in a needle guide tube (and usual care). Thus, by using carefully designed placebos, researchers can isolate the effects of some CAM therapies on the overall clinical response. For CAM therapies to be considered efficacious, evidence must show that they are more efficacious than placebo.

  • 1Takakura N, Yajima H: A placebo acupuncture needle with potential for double blinding—a validation study. Acupunct Med 26(4):224–230, 2008.

  • 2Cherkin DC, Sherman KJ, Avins AL, et al: A randomized trial comparing acupuncture, simulated acupuncture, and usual care for chronic low back pain. Arch Intern Med169(9):858–66, 2009.


Although the safety of most CAM therapies has not been studied in clinical trials, many of these therapies have a good safety record. Many CAM therapies (eg, nontoxic botanicals, mind-body techniques such as meditation and yoga, body-based practices such as massage) have been used for thousands of years with no evidence of harm, and many seem to have no potential for harm. However, there are some safety considerations, including the following:

  • Use of an alternative approach to treat a life-threatening disorder that can be effectively treated conventionally (eg, meningitis, diabetic ketoacidosis, acute leukemia)—perhaps the greatest risk of CAM, rather than the risk of direct harm from a CAM therapy

  • Toxicity from certain herbal preparations (eg, hepatotoxicity from pyrrolizidine alkaloids, Atractylis gummifera, chaparral, germander, greater celandine, Jin Bu Huan, kava, pennyroyal, or others; nephrotoxicity from Aristolochia; adrenergic stimulation from ephedra)

  • Contamination (eg, heavy metal contamination of some Chinese and Ayurvedic herbal preparations; contamination of other products, such as PC-SPES and some Chinese herbs, with other drugs)

  • Interactions between CAM therapies (eg, botanicals, micronutrients, other dietary supplements) and other drugs (eg, induction of cytochrome P-450 [CYP3A4] enzymes by St. John’s wort, resulting in reduced activity of antiretrovirals, immunosuppressants, and other drugs), particularly when the drug has a narrow therapeutic index

  • As with any physical manipulation of the body (including mainstream techniques such as physical therapy), injury (eg, nerve or cord damage due to spinal manipulation in patients at risk, bruising in patients with bleeding disorders)

Current alerts about harmful dietary supplements are available at the FDA web site (Safety Alerts and Advisories). Historically, the FDA did not tightly regulate the production of dietary supplements. However, new FDA regulations now require compliance with manufacturing practices that guarantee quality and safety of supplements.

To help prevent injuries due to physical manipulations, patients should look for CAM practitioners who graduated from accredited schools and are professionally licensed. Rates of complications are very low when chiropractic or acupuncture is provided by practitioners with full credentials.

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