Efficacy

Alternative therapies lack the requisite scientific validation, and their effectiveness is either unproved or disproved.^{[1][99][106][107]} Many of the claims regarding the efficacy of alternative medicines are controversial, since research on them is frequently of low quality and methodologically flawed.^[110] Selective publication of results misleading results from only publishing positive results, and not all results, marked differences in product quality and standardisation, and some companies making unsubstantiated claims, call into question the claims of efficacy of isolated examples where herbs may have some evidence of containing chemicals that may affect health.^[172] The Scientific Review of Alternative Medicine points to confusions in the general population - a person may attribute symptomatic relief to an otherwise-ineffective therapy just because they are taking something the placebo effect; the natural recovery from or the cyclical nature of an illness the regression fallacy gets misattributed to an alternative medicine being taken; a person not diagnosed with science based medicine may never originally have had a true illness diagnosed as an alternative disease category.^[173]

Edzard Ernst characterized the evidence for many alternative techniques as weak, nonexistent, or negative^[143] and in 2011 published his estimate that about 7.4% were based on "sound evidence", although he believes that may be an overestimate due to various reasons.^[174] Ernst has concluded that 95% of the alternative treatments he and his team studied, including acupuncture, herbal medicine, homeopathy, and reflexology, are "statistically indistinguishable from placebo treatments", but he also believes there is something that conventional doctors can usefully learn from the chiropractors and homeopath: this is the therapeutic value of the placebo effect, one of the strangest phenomena in medicine.^[175][176]

In 2003, a project funded by the CDC identified 208 condition-treatment pairs, of which 58% had been studied by at least one randomized controlled trial RCT, and 23% had been assessed with a meta-analysis.^[177] According to a 2005 book by a US Institute of Medicine panel, the number of RCTs focused on CAM has risen dramatically. The book cites Vickers 1998, who found that many of the CAM-related RCTs are in the Cochrane register, but 19% of these trials were not in MEDLINE, and 84% were in conventional medical journals.^[178]

As of 2005, the Cochrane Library had 145 CAM-related Cochrane systematic reviews and 340 non-Cochrane systematic reviews. An analysis of the conclusions of only the 145 Cochrane reviews was done by two readers. In 83% of the cases, the readers agreed. In the 17% in which they disagreed, a third reader agreed with one of the initial readers to set a rating. These studies found that, for CAM, 38.4% concluded positive effect or possibly positive 12.4%, 4.8% concluded no effect, 0.69% concluded harmful effect, and 56.6% concluded insufficient evidence. An assessment of conventional treatments found that 41.3% concluded positive or possibly positive effect, 20% concluded no effect, 8.1% concluded net harmful effects, and 21.3% concluded insufficient evidence. However, the CAM review used the more developed 2004 Cochrane database, while the conventional review used the initial 1998 Cochrane database.^[179]

Most alternative medical treatments are not patentable, which may lead to less research funding from the private sector. In addition, in most countries, alternative treatments in contrast to pharmaceuticals can be marketed without any proof of efficacy—also a disincentive for manufacturers to fund scientific research.^[180] Some have proposed adopting a prize system to reward medical research.^[181] However, public funding for research exists. Increasing the funding for research on alternative medicine techniques is the purpose of the US National Center for Complementary and Alternative Medicine. NCCAM and its predecessor, the Office of Alternative Medicine, have spent more than $2.5 billion on such research since 1992; this research has largely not demonstrated the efficacy of alternative treatments.^{[135][182][183]}

In the same way as for conventional therapies, drugs, and interventions, it can be difficult to test the efficacy of alternative medicine in clinical trials. In instances where an established, effective, treatment for a condition is already available, the Helsinki Declaration states that withholding such treatment is unethical in most circumstances. Use of standard-of-care treatment in addition to an alternative technique being tested may produce confounded or difficult-to-interpret results.^[184]

Cancer researcher Andrew J. Vickers has stated:

"Contrary to much popular and scientific writing, many alternative cancer treatments have been investigated in good-quality clinical trials, and they have been shown to be ineffective. In this article, clinical trial data on a number of alternative cancer cures including Livingston-Wheeler, Di Bella Multitherapy, antineoplastons, vitamin C, hydrazine sulfate, Laetrile, and psychotherapy are reviewed. The label 'unproven' is inappropriate for such therapies; it is time to assert that many alternative cancer therapies have been 'disproven'."^[185]

Homeopathy is based on the belief that a disease can be cured by a very low dose of substance that creates similar symptoms in a healthy person.^{[186][n 17]} This conflicts with fundamental concepts of physics and chemistry and there is no good evidence from reviews of research to support its use.^{[188][189][190][191]}