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According to the Chiropractors’ Association of Australia (CAA, n.d.), chiropractic is a healthcare system which focuses on the relationship between the skeletal structure, the nervous system, and health, and is primarily achieved through spinal manipulation. It is a big industry, with practices established in over 70 countries (National Board of Chiropractic Examiners, n.d.). Australian chiropractors are five year university-trained (CAA), and in 2004-05 they received over 215,000 consultations per week (ABS, 2006). Yet despite chiropractic’s pervasiveness there is considerable debate over its standing as a mainstream healthcare system. The debate is so vitriolic that one chiropractor even wrote “Have an early death. No one will miss you” in response to one of many online articles by a doctor referring to chiropractic as quackery (“Cheers and Jeers”, 2009). What causes people of education and community standing to fall to levels such as this? Despite criticism, why is chiropractic still popular? In an attempt to address such questions, this essay will separate the issues, and examine how people evaluate contradictory information.
Issue 1: The Validity of Chiropractic
The first issue revolves around the theme that chiropractors use techniques that are unscientific and lacking empirical support. When Palmer developed chiropractic at the beginning of the twentieth century he asserted that the body had an “innate intelligence” that allowed it to heal itself, and obstruction of this innate energy to nerves by “vertebral subluxations” (misaligned or dysfunctional joints) could result in pain and internal disease (Keating Jr., Cleveland III, & Menke, 2005). However, critics claim that there is no evidence for this innate mechanism (Mirtz, Morgan, Wyatt, & Greene, 2009). Furthermore, they point not only to the lack of any causal relationship between vertebral subluxations and disease, but also to the lack of evidence for the very existence of the subluxations (e.g. Ernst, 2008).
Supporters of chiropractic seize upon the fact that Palmer’s hypotheses have not been disproven. In the face of ambiguous information, they interpret events according to their beliefs. For example, the president of the American Chiropractic Association wrote that “Scientific research presently is not sophisticated enough to determine the neurophysiological impact that spinal subluxation has on our patients” (Lynch, 1995, as cited in Keating Jr. et al., 2005, p. 3) – making the assumption that the hypothesis is in fact real. Indeed, chiropractic organisations around the world incorporate the concept of subluxations into their core identities (Keating Jr. et al.). The high costs associated with this house-of-cards approach being disproven, along with the desire to remain within the group, would strongly motivate chiropractors to exaggerate the amount of support for their beliefs.
The representativeness heuristic can be applied to demonstrate a cognitive factor which accentuates chiropractors’ beliefs in the validity of their profession. The more one event resembles another, the greater the probability of it being assigned as such (Gilovich, 1991). Thus the more chiropractic represents mainstream medicine, the greater the association with the validity of established medicine. This could explain a survey by Redwood, Hawk, Cambron, Vinjamury, and Bedard (2008) which found that 27% of chiropractors preferred their profession to be categorised as “integrated medicine” rather than “complementary and alternative medicine”. Furthermore, some chiropractors have established themselves as “whole health” practitioners, offering advice on vaccinations, nutrition, and lifestyle and weight loss management (Ernst, 2008).
It is likely that critics of chiropractic underestimate the degree to which their own beliefs contributed to their judgements. A number of critics would likely reside in established medicine, and would also be aware of the American Medical Association’s labelling of chiropractic as unscientific and cultist, and its failed attempts to eliminate chiropractic during the period from the 1960s to the 1980s (Keating Jr., Cleveland III, & Menke, 2005). Surely this knowledge would influence pre-existing beliefs, and easily bias people to exaggerate the amount of support for their beliefs.
Adding to the distortion is the desire to see what one wants to see. Although published information can be accurate (e.g. peer-reviewed journals), the information is still second-hand, and open to bias. For example, in one article critical of chiropractic, Ernst (2008) wrote of the hostile opposition of current chiropractic literature to immunisation – but how many readers would have dug deeper to find that his source was from 1992? (A study by Russell, Injeyan, Verhoef, and Eliasziw, 2004, found chiropractors are just as likely to advise for immunisation as to advise against it).
Issue 2: The Dangers of Chiropractic
The second issue is that critics believe that chiropractic treatment is dangerous because there can be adverse effects. Firstly, studies have shown that there can be increased discomfort, including increased pain, headaches, stiffness, and fatigue (e.g. Hurwitz, Morgenstern, Vassilaki, & Chiang, 2004). Secondly, studies, including a meta-analysis by Miley, Wellik, Wingerchuk, and Demaerschalk (2008) have found an association between cervical manipulative therapy and stroke. Thirdly, Ernst’s (2010) literature review found 26 fatalities associated with chiropractic treatment since 1934. In contrast, supporters of chiropractic believe that the risks are small or non-existent, and that the dangers are comparable with other treatments. For example, a study by Cassidy et al. (2008) concluded that strokes may be a pre-existing condition and that the risks of chiropractic treatment are no greater than that for other treatment.
Both sides face contradictory data, and yet they continue to strongly support their positions. A cognitive factor which could accentuate and distort opinions is ignoring base rates. Barrett (2009) described numerous reports showing an association between chiropractic and strokes, but there is no mention of the rates of adverse reactions to alternative treatments. If a judgement is to be made whether chiropractic treatment is preferable to an alternative treatment, base rate information on adverse effects for both contingencies is essential.
Beliefs can also be distorted by the biasing effects of second-hand information. For example, a recent article in The Australian was titled “Chiropractors ‘could increase stroke risk.’” (2010, Sep. 8). However, further reading revealed that the researcher who made the claim had completed a study which found an unrelated conclusion (that milder therapy was just as effective at alleviating neck pain as was manipulation). When asserting that chiropractors could increase stroke risk, he was merely referring to previous studies which found an association between manipulation and stroke, and made no mention of the studies which opposed those findings.
In the face of contradictory data, chiropractors have been known to reject, ignore or reinterpret them. In one example, the chairman of the U.K. General Chiropractic Council referred to adverse findings of spinal manipulation by Ernst (2007) as a “scare story” (Dixon, 2007, para. 4). In another example, despite numerous studies detailing the risk of strokes arising from spinal manipulation, and the qualified finding of no evidence from Cassidy et al. (2008), the Connecticut Chiropractic Board concluded that there was no risk (“Connecticut chiropractors”, 2010). Others appear to massage the data: not rejecting the findings, but instead deciding that random outcomes can occur (e.g. Reggars, 2010).
Issue 3: The Efficacy of Chiropractic
The third issue is that there is contradictory evidence for the efficacy of spinal manipulation. Some believe that chiropractic is not better than other treatments. For example, a meta-analysis by Assendelft, Morton, Yu, Suttorp, and Shekelle (2003) found spinal manipulative therapy to be no better than general practitioner care, analgesics, physical therapy, and exercises. However, supporters believe the opposite. For example, research by Haas, Bronfort, and Evans (2006) on mainly randomised control trials (RCTs) found that spinal manipulative therapy is: superior to medication and placebos; superior to or equivalent to mobilisation for various forms of lower back pain; equivalent to mobilisation for neck pain; and has mixed results for headaches.
Both sides face contradictory data, and yet they continue to strongly support their positions. A number of cognitive factors can be identified which could accentuate and distort opinions. Firstly, proponents of chiropractic may ignore regression to the mean and not consider the fact that users would see a chiropractor when their pain was highest and that it probably would have reduced anyway. Belief in the efficacy of chiropractic could also be enhanced by the tendency not to seek non-confirmatory information (Gilovich, 1991) – it is unlikely that chiropractic users would test the contingency that they could get better even if they do not get treated. Thirdly, the representativeness heuristic can influence supporters by encouraging the association of physical problems with physical manipulation, and influence critics by encouraging chiropractic to be seen as representative of other, less scientific, complementary and alternative medicines such as homeopathy. Fourthly, placebo effects of the “pop” sound and human contact from a manipulation would likely reinforce users’ judgements of success. Fifthly, both critics and supporters with professional backgrounds would be likely to have self-confirming bias. For example, they would be more likely to read their own journals that would be less likely to criticise their own position. Even the National Board of Chiropractic Examiners (n.d.) is guilty of encouraging bias: their report titled “Studies of Chiropractic” failed to include any negative findings, and glossed over mixed findings. Biases like these would make people vulnerable to the availability heuristic, because they would more readily bring to mind information supportive of their own position.
Motivational factors can also distort beliefs. Firstly, people are influenced by second-hand information, which can be biased (Gilovich, 1991). Xue et al. (2008) found that 43.6% of Australian users were referred by friends or relatives, and it is likely that these referrers would have endorsed the benefits of chiropractic. Secondly, people from both sides are likely to interact with people of similar beliefs and, through the false consensus effect (Gilovich), will be likely to assume that their beliefs are more supported than they actually are. Furthermore, people often over-estimate their own abilities (Gilovich), so those that belong to the scientific community are likely to have strong beliefs in their own statistical and research skills, and even extend those beliefs to the scientific group to which they belong. Therefore it is highly likely that they will accept research findings by their group concerning the effectiveness of chiropractic without questioning them much as they should. Moreover, if indeed beliefs are possessions (Gilovich), then these people are likely to take contradictory information as a personal affront, and react negatively and emotionally, as seen in the responses to the Chirobase website.
In the face of contradictory data, supporters of chiropractic have attacked them on methodological grounds. They argue that the RCT approach is difficult to implement with complementary and alternative medicine, because of difficulties with finding appropriate placebos, and the difficulties in randomisation due to expectancy effects and individual differences in diagnoses (Verhoef et al., 2005). A proposed alternative is “whole systems research,” which focuses more on patient-based outcomes (Hawk, Khorsan, Lisi, Ferrance, & Evans, 2007). However, even this creates opportunities for distorted beliefs because it increases the likelihood of unfocused outcomes and hence confirmation bias.
Where to from here?
The debate appears set to continue for some time. Although both sides trade RCT studies and conduct meta-analyses, the results are only as good as the methodologies. Consequently there is much ambiguity and many opportunities for distortions of beliefs, as can be seen in numerous media and websites. Although there is a growing recognition from the chiropractic profession that change is required, it is not doing itself any favours by remaining fragmented. There is a lack of international guidelines, they are not playing a progressive role in public health, and they are not taking a clear stand on the status of the scientific underpinnings of their techniques (Murphy, Schneider, Seaman, Perle, & Nelson, 2008). What is required is firstly a commitment to be aware that although people value being rational, many factors can distort opinions and judgements; and secondly, a commitment to more rigorous studies with agreed-upon methodologies and outcome criteria. These are essential, because the cost of erroneous beliefs could be high: people in pain may not obtain the most effective treatment, jobs are at stake, and most importantly, lives may be lost or saved.
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