Complementary medicine: Where is the evidence?

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Applied Evidence

Complementary medicine: Where is the evidence?

J Fam Pract. 2003 August;52(8):630-634

By

Edzard Ernst, MD, PhD, FRCP

(Edin.)

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References

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14. Linde K, Willich SN. How objective are systematic reviews? Differences between reviews on complementary medicine. J R Soc Med 2003;96:17-22.

15. Ernst E. How objective are systematic reviews? J R Soc Med 2003;96:56-57.

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22. Vickers A, Cassileth B, Ernst E, et al. How should we research unconventional therapies? A panel report from the conference on Complementary and Alternative Medicine Research Methodology, National Institute of Health. Int J Technol Assess Health Care 1997;13:111-121.

23. Ernst E, Pittler MH, Stevinson C, White AR. The desktop guide to complementary and alternative medicine. London: Mosby; 2001.

24. Bloom BS, Retbi A, Dahan S, Jonsson E. Evaluation of randomized controlled trials on complementary and alternative medicine. Int J Technol Assess Health Care 2000;16:13-21.

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Practice recommendations

Herbal medicines have been submitted to systematic reviews more frequently than any other complementary therapy, and it is here where the most positive evidence can be found.
There is not much research into potential serious risks of complementary medicine. Possible risks range from the toxicity of herbs to vertebral artery dissection or nerve damage after chiropractic manipulation.
Currently the Cochrane Library contains 34 systematic reviews of complementary medicine: 20 of herbal medicines, 7 of acupuncture, 3 of homeopathy, 2 of manual therapies, and 2 of other forms.

Complementary or alternative medicine has moved from the fringe of health care toward its center; recent figures show that in Germany, for instance, no less than three quarters of the general population use at least 1 complementary therapy.¹ In the United States, the equivalent figures have increased from 33% in 1990 to 42% in 1997.²

Virtually all survey data agree that those most fascinated with complementary medicine are predominantly female, affluent, middleaged, and well-educated. Seventy-eight percent of all Medicaid programs provide coverage of at least 1 form of complementary medicine.³

At the same time, critics of complementary medicine often insist there is no good evidence to support these therapies,^4,5 and that it is a waste of resources and a misuse of science to try establishing an evidence base for therapies that are essentially nonscientific, irrational, and implausible fads.⁶ But is this really true?

Research in complementary medicine

Over the last 30 years, the level of original research activity in complementary medicine has increased considerably.⁷ The best quality of evidence for or against the effectiveness of any therapy is usually provided by Cochrane reviews.^8,9

Cochrane reviews

Currently the Cochrane Library contains 34 systematic reviews and 35 protocols of complementary medicine¹⁰ (depending on what one considers complementary/alternative and what mainstream, this figure might vary marginally). Twenty of the reviews are of herbal medicines, 7 of acupuncture, 3 of homeopathy, 2 of manual therapies, and 2 of other forms of comple-mentary medicine. Twelve reviews include a meta-analytic approach.

The 34 reviews comprise a total of 286 clinical, mostly randomized and often placebo-controlled, double-blind studies. In 1999, the Cochrane Library listed more than 4000 controlled trials of complementary medicine and a further 4000 awaited assessment.¹¹

The single largest Cochrane review of complementary medicine is a meta-analysis of randomized clinical trials of St John’s wort for depression, based on 27 primary studies with a total of 2291 patients.¹² Seven of the 34 Cochrane reviews are “negative”ie, do not suggest a positive clinical effect of the intervention under evaluation. Eleven are entirely inconclusive and 16 draw at least tentatively positive conclusions (Table). Given the dire funding situation for research in complementary medicine,¹³ this evidence base is remarkable.

TABLE
Cochrane reviews in complementary medicine with (tentatively) positive results

First author (primary studies)*	Therapy	Indication	Reservations*
Furlan (8)	Massage	Low back pain	More studies required, some trials of poor quality
Green (4)	Acupuncture	Lateral elbow pain	More studies required, most trials of poor quality
Linde (7)	Acupuncture	Asthma	Evidence only positive for peak expiratory flow rate, effect size small
Linde (27)	St John’s wort (Hypericum perforatum)^†	Depression	Some trials of poor quality, few equivalence studies
Little (11)	Various herbal medicines	Rheumatoid arthritis	More studies required, some trials of poor quality
Little (5)	Various herbal medicines	Osteoarthritis	More studies required, some trials of poor quality
Melchart (26)	Acupuncture	Headache	Evidence positive only for migraine headaches, effect size small
Pittler (7)	Kava (Piper methysticum)^†	Anxiety	Concern over safety
Pittler (13)	Horse chestnut (Aesculus hippocastanum)^†	Chronic venous insufficiency	Scarcity of long-term studies
Pittler (4)	Feverfew (Tanacetum parthenium)^†	Migraine prevention	More studies required, effect size small
Pittler (2)	Globe artichoke (Cynara scolymus)^†	Hypercholesterolemia	More studies required effect size small
Vickers (7)	Oscillococcinum	Influenza	More studies required, effect size small
Wilt (21)	Saw palmetto (Serenoa repens)^†	Benign prostate hypertrophy	Effect size moderate, scarcity of long-term studies
Wilt (18)	African prune (Pygeum africanum)^†	Benign prostate hypertrophy	Scarcity of long-term studies
Wilt (4)	Cernilton^†	Benign prostate hypertrophy	More studies required, scarcity of long-term trials
Wilt (4)	Beta-sitosterols^†	Benign prostate hypertrophy	More studies required, scarcity of long-term trials
All data extracted from The Cochrane Library, 2003. “More studies required” means that volume of data was small; “trials of poor quality” means that the average quality of the evidence was lowered by flawed studies; “effect size” describes the difference in clinical response to active and control treatment.
*As expressed by authors of respective review.
†Plant-based treatments.

Other reviews

The Cochrane database may be the best but certainly is not the only source of systematic reviews of complementary medicine. My unit has published about 100 systematic reviews (a full list is available from the author), and most were not in the Cochrane format.

Linde and Willich have analyzed selected systematic reviews of acupuncture, homeopathy, and herbal medicine, and have shown that their methodological approach differed considerably.¹⁴

Methods of reviewing complementary medicine

The conclusions of these methodologically diverse articles were still surprisingly consistent.¹⁵ Some maintain that complementary medicine cannot be evidence-based in the conventional sense of the word¹⁶ ; that “softer” types of evidence need to be taken into consideration as well¹⁷ ; that placebo effects must not be dismissed as nonbeneficial¹⁸ ; that the healing encounter includes significant factors that may never be quantifiable¹⁹ ; that “the scientific method cannot measure hope, divine intervention, or the power of belief.”²⁰ And, obviously, research in complementary medicine “must consider social, cultural, political, and economic contexts.”²¹