A reader of this blog recently sent me the following message: “Looks like this group followed you recent post about how to perform a CAM RCT!” A link directed me to a new trial of ear-acupressure. Today is ‘national acupuncture and oriental medicine day’ in the US, a good occasion perhaps to have a critical look at it.
The aim of this study was to assess the effectiveness of ear acupressure and massage vs. control in the improvement of pain, anxiety and depression in persons diagnosed with dementia.
For this purpose, the researchers recruited a total of 120 elderly dementia patients institutionalized in residential homes. The participants were randomly allocated, to three groups:
- Control group – they continued with their routine activities;
- Ear acupressure intervention group – they received ear acupressure treatment (pressure was applied to acupressure points on the ear);
- Massage therapy intervention group – they received relaxing massage therapy.
Pain, anxiety and depression were assessed with the Doloplus2, Cornell and Campbell scales. The study was carried out during 5 months; three months of experimental treatment and two months with no treatment. The assessments were done at baseline, each month during the treatment and at one and two months of follow-up.
A total of 111 participants completed the study. The ear acupressure intervention group showed better improvements than the two other groups in relation to pain and depression during the treatment period and at one month of follow-up. The best improvement in pain was achieved in the last (3rd) month of ear acupressure treatment. The best results regarding anxiety were also observed in the last month of treatment.
The authors concluded that ear acupressure and massage therapy showed better results than the control group in relation to pain, anxiety and depression. However, ear acupressure achieved more improvements.
The question is: IS THIS A RIGOROUS TRIAL?
My answer would be NO.
Now I better explain why, don’t I?
If we look at them critically, the results of this trial might merely prove that spending some time with a patient, being nice to her, administering a treatment that involves time and touch, etc. yields positive changes in subjective experiences of pain, anxiety and depression. Thus the results of this study might have nothing to do with the therapies per se.
And why would acupressure be more successful than massage therapy? Massage therapy is an ‘old hat’ for many patients; by contrast, acupressure is exotic and relates to mystical life forces etc. Features like that have the potential to maximise the placebo-response. Therefore it is conceivable that they have contributed to the superiority of acupressure over massage.
What I am saying is that the results of this trial can be interpreted in not just one but several ways. The main reason for that is the fact that the control group were not given an acceptable placebo, one that was indistinguishable from the real treatment. Patients were fully aware of what type of intervention they were getting. Therefore their expectations, possibly heightened by the therapists, determined the outcomes. Consequently there were factors at work which were totally beyond the control of the researchers and a clear causal link between the therapy and the outcome cannot be established.
An RCT that is aimed to test the effectiveness of a therapy but fails to establish such a causal link beyond reasonable doubt cannot be characterised as a rigorous study, I am afraid.
Sorry! Did I spoil your ‘national acupuncture and oriental medicine day’?
Hard to believe that it’s been already two years! On 14 October 2012, I posted the very first article. It set out what I wanted to achieve:
Why another blog offering critical analyses of the weird and wonderful stuff that is going on in the world of alternative medicine? The answer is simple: compared to the plethora of uncritical misinformation on this topic, the few blogs that do try to convey more reflected, sceptical views are much needed; and the more we have of them, the better.
At the time, I had no idea how successful this venture into the unknown would become. Today, over 350 articles have been posted and almost 8000 comments have contributed to an often lively debate about almost all aspects of alternative medicine. Currently, the blog has well over 1000 – 2000 visitors every day. Selected posts have been translated and re-published in about half a dozen languages. I admit: I am quite proud of all that!
Back in 2012, I also had no idea how much fun I would derive from doing all this. Those who know me well would probably confirm that I am an unlikely candidate for getting his teeth into something like a blog. Thanks to mostly helpful and often brilliant comments from my readers, this blog has become a constant source of entertainment and information for me and, I hope, many others too.
My aims have remained very much the same during these last two years. Today I might formulate them as follows:
- I want to inform the public about all matters related to alternative medicine.
- I aim to review new evidence as it emerges.
- I also wish to entertain my readers.
- I feel a strong need to create a counter-balance to the thousands of blogs that are dangerously promotional and woefully uncritical.
- And I want to help consumers to become much more effective ‘BULL-SHIT DETECTORS’ (I got this term recently from Sir Iain Chalmers).
Of course, none of these aims are achievable without active, critical, witty and outspoken readers and commentators. I would like to take the occasion of this second anniversary to thank everybody who has helped with and contributed to this blog. May the good work and intense fun continue!
‘Healing, hype or harm? A critical analysis of complementary or alternative medicine’ is the title of a book that I edited and that was published in 2008. Its publication date coincided with that of ‘Trick or Treatment?’ and therefore the former was almost completely over-shadowed by the latter. Consequently few people know about it. This is a shame, I think, and this post is dedicated to encouraging my readers to have a look at ‘Healing, hype or harm?’
One reviewer commented on Amazon about this book as follows: Vital and informative text that should be read by everyone alongside Ben Goldacre’s ‘Bad Science’ and Singh and Ernt’s ‘Trick or Treatment’. Everyone should be able to made informed choices about the treatments that are peddled to the desperate and gullible. As Tim Minchin famously said ‘What do you call Alternative Medicine that has been proved to work? . . . Medicine!’
This is high praise indeed! But I should not omit the fact that others have commented that they were appalled by our book and found it “disappointing and unsettling”. This does not surprise me in the least; after all, alternative medicine has always been a divisive subject.
The book was written by a total of 17 authors and covers many important aspects of alternative medicine. Some of its most famous contributors are Michael Baum, Gustav Born, David Colquhoun, James Randi and Nick Ross. Some of the most important subjects include:
As already mentioned, our book is already 6 years old; however, this does not mean that it is now out-dated. The subject areas were chosen such that it will be timely for a long time to come. Nor does this book reflect one single point of view; as it was written by over a dozen different experts with vastly different backgrounds, it offers an entire spectrum of views and attitudes. It is, in a word, a book that stimulates critical thinking and thoughtful analysis.
I sincerely think you should have a look at it… and, in case you think I am hoping to maximise my income by telling you all this: all the revenues from this book go to charity.
One of the most commonly ‘accepted’ indications for acupuncture is anxiety. Many trials have suggested that it is effective for that condition. But is this really true? To find out, we need someone to conduct a systematic review or meta-analysis.
Korean researchers have just published such a paper; they wanted to assess the preoperative anxiolytic efficacy of acupuncture therapy and therefore conducted a meta-analysis of all RCTs on the subject. Four electronic databases were searched up to February 2014. Data were included in the meta-analysis from RCTs in which groups receiving preoperative acupuncture treatment were compared with control groups receiving a placebo for anxiety.
Fourteen publications with a total of 1,034 patients were included. Six RCTs, using the State-Trait Anxiety Inventory-State (STAI-S), reported that acupuncture interventions led to greater reductions in preoperative anxiety relative to sham acupuncture. A further eight publications, employing visual analogue scales, also indicated significant differences in preoperative anxiety amelioration between acupuncture and sham acupuncture.
The authors concluded that aacupuncture therapy aiming at reducing preoperative anxiety has a statistically significant effect relative to placebo or nontreatment conditions. Well-designed and rigorous studies that employ large sample sizes are necessary to corroborate this finding.
From these conclusions most casual readers might get the impression that acupuncture is indeed effective. One has to dig a bit deeper to realise that is perhaps not so.
Why? Because the quality of the primary studies was often dismally poor. Most did not even mention adverse effects which, in my view, is a clear breach of publication ethics. What is more, all the studies were wide open to bias. The authors of the meta-analysis include in their results section the following short paragraph:
The 14 included studies exhibited various degrees of bias susceptibility (Figure 2 and Figure 3). The agreement rate, as measured using Cohen’s kappa, was 0.8 . Only six studies reported concealed allocation; the other six described a method of adequate randomization, although the word “randomization” appeared in all of the articles. Thirteen studies prevented blinding of the participants. Participants in these studies had no previous experience of acupuncture. According to STRICTA, two studies enquired after patients’ beliefs as a group: there were no significant differences [20, 24].
There is a saying amongst experts about such meta-analyses: RUBBISH IN, RUBBISH OUT. It describes the fact that several poor studies, pooled meta-analytically, can never give a reliable result.
This does, however, not mean that such meta-analyses are necessarily useless. If the authors prominently (in the abstract) stress that the quality of the primary studies was wanting and that therefore the overall result is unreliable, they might inspire future researchers to conduct more rigorous trials and thus generate progress. Most importantly, by insisting on pointing out these limitations and by not drawing positive conclusions from flawed data, they would avoid misleading those health care professionals – and let’s face it, they are the majority – who merely read the abstract or even just the conclusions of such articles.
The authors of this review have failed to do any of this; they and the journal EBCAM have thus done a disservice to us all by contributing to the constant drip of misleading and false-positive information about the value of acupuncture.
After the usually challenging acute therapy is behind them, cancer patients are often desperate to find a therapy that might improve their wellbeing. At that stage they may suffer from a wide range of symptoms which can seriously limit their quality of life. Any treatment that can be shown to restore them to their normal mental and physical health would be more than welcome.
Most homeopaths believe that their remedies can do just that, particularly if they are tailored not to the disease but to the individual patient. Sadly, the evidence that this might be so is almost non-existent. Now, a new trial has become available; it was conducted by Jennifer Poole, a chartered psychologist and registered homeopath, and researcher and teacher at Nemeton Research Foundation, Romsey.
The aim of this study was to explore the benefits of a three-month course of individualised homeopathy (IH) for survivors of cancer. Fifteen survivors of any type of cancer were recruited from a walk-in cancer support centre. Conventional treatment had to have taken place within the last three years. Patients saw a homeopath who prescribed IH. After three months of IH, they scored their total, physical and emotional wellbeing using the Functional Assessment of Chronic Illness Therapy for Cancer (FACIT-G). The results show that 11 of the 14 women had statistically positive outcomes for emotional, physical and total wellbeing.
The conclusions of the author are clear: Findings support previous research, suggesting CAM or IH could be beneficial for survivors of cancer.
This article was published in the NURSING TIMES, and the editor added a footnote informing us that “This article has been double-blind “.
I find this surprising. A decent peer-review should have picked up the point that a study of that nature cannot possibly produce results which tell us anything about the benefits of IH. The reasons for this are fairly obvious:
- there was no control group,
- therefore the observed outcomes are most likely due to 1) natural history, 2) placebo, 3) regression towards the mean and 4) social desirability; it seems most unlikely that IH had anything to do with the result
- the sample size was tiny,
- the patients elected to receive IH which means that had high expectations of a positive outcome,
- only subjective outcome measures were used,
- there is no good previous research suggesting that IH benefits cancer patients.
On the last point, a recent systematic review showed that the studies available on this topic had mixed results either showing a significantly greater improvement in QOL in the intervention group compared to the control group, or no significant difference between groups. The authors concluded that there existed significant gaps in the evidence base for the effectiveness of CAM on QOL in cancer survivors. Further work in this field needs to adopt more rigorous methodology to help support cancer survivors to actively embrace self-management and effective CAMs, without recommending inappropriate interventions which are of no proven benefit.
All this new study might tell us is that IH did not seem to harm these patients – but even this finding is not certain; to be sure, we would need to include many more patients. Any conclusions about the effectiveness of IH are totally unwarranted. But are there ANY generalizable conclusions that can be drawn from this article? Yes, I can think of a few:
- Some cancer patients can be persuaded to try the most implausible treatments.
- Some journals will publish any rubbish.
- Some peer-reviewers fail to spot the most obvious defects.
- Some ‘researchers’ haven’t got a clue.
- The attempts of misleading us about the value of homeopathy are incessant.
One might argue that this whole story is too trivial for words; who cares what dodgy science is published in the NURSING TIMES? But I think it does matter – not so much because of this one silly article itself, but because similarly poor research with similarly ridiculous conclusions is currently published almost every day. Subsequently it is presented to the public as meaningful science heralding important advances in medicine. It matters because this constant drip of bogus research eventually influences public opinion and determines far-reaching health care decisions.
Many proponents of alternative medicine seem somewhat suspicious of research; they have obviously understood that it might not produce the positive result they had hoped for; after all, good research tests hypotheses and does not necessarily confirm beliefs. At the same time, they are often tempted to conduct research: this is perceived as being good for the image and, provided the findings are positive, also good for business.
Therefore they seem to be tirelessly looking for a study design that cannot ‘fail’, i.e. one that avoids the risk of negative results but looks respectable enough to be accepted by ‘the establishment’. For these enthusiasts, I have good news: here is the study design that cannot fail.
It is perhaps best outlined as a concrete example; for reasons that will become clear very shortly, I have chosen reflexology as a treatment of diabetic neuropathy, but you can, of course, replace both the treatment and the condition as it suits your needs. Here is the outline:
- recruit a group of patients suffering from diabetic neuropathy – say 58, that will do nicely,
- randomly allocate them to two groups,
- the experimental group receives regular treatments by a motivated reflexologist,
- the controls get no such therapy,
- both groups also receive conventional treatments for their neuropathy,
- the follow-up is 6 months,
- the following outcome measures are used: pain reduction, glycemic control, nerve conductivity, and thermal and vibration sensitivities,
- the results show that the reflexology group experience more improvements in all outcome measures than those of control subjects,
- your conclusion: This study exhibited the efficient utility of reflexology therapy integrated with conventional medicines in managing diabetic neuropathy.
This method is fool-proof, trust me, I have seen it often enough being tested, and never has it generated disappointment. It cannot fail because it follows the notorious A+B versus B design (I know, I have mentioned this several times before on this blog, but it is really important, I think): both patient groups receive the essential mainstream treatment, and the experimental group receives a useless but pleasant alternative treatment in addition. The alternative treatment involves touch, time, compassion, empathy, expectations, etc. All of these elements will inevitably have positive effects, and they can even be used to increase the patients’ compliance with the conventional treatments that is being applied in parallel. Thus all outcome measures will be better in the experimental compared to the control group.
The overall effect is pure magic: even an utterly ineffective treatment will appear as being effective – the perfect method for producing false-positive results.
And now we hopefully all understand why this study design is so very popular in alternative medicine. It looks solid – after all, it’s an RCT!!! – and it thus convinces even mildly critical experts of the notion that the useless treatment is something worth while. Consequently the useless treatment will become accepted as ‘evidence-based’, will be used more widely and perhaps even reimbursed from the public purse. Business will be thriving!
And why did I employ reflexology for diabetic neuropathy? Is that example not a far-fetched? Not a bit! I used it because it describes precisely a study that has just been published. Of course, I could also have taken the chiropractic trial from my last post, or dozens of other studies following the A+B versus B design – it is so brilliantly suited for misleading us all.
On this blog, I have often pointed out how dismally poor most of the trials of alternative therapies frequently are, particularly those in the realm of chiropractic. A brand-new study seems to prove my point.
The aim of this trial was to determine whether spinal manipulative therapy (SMT) plus home exercise and advice (HEA) compared with HEA alone reduces leg pain in the short and long term in adults with sub-acute and chronic back-related leg-pain (BRLP).
Patients aged 21 years or older with BRLP for least 4 weeks were randomised to receive 12 weeks of SMT plus HEA or HEA alone. Eleven chiropractors with a minimum of 5 years of practice experience delivered SMT in the SMT plus HEA group. The primary outcome was subjective BRLP at 12 and 52 weeks. Secondary outcomes were self-reported low back pain, disability, global improvement, satisfaction, medication use, and general health status at 12 and 52 weeks.
Of the 192 enrolled patients, 191 (99%) provided follow-up data at 12 weeks and 179 (93%) at 52 weeks. For leg pain, SMT plus HEA had a clinically important advantage over HEA (difference, 10 percentage points [95% CI, 2 to 19]; P = 0.008) at 12 weeks but not at 52 weeks (difference, 7 percentage points [CI, -2 to 15]; P = 0.146). Nearly all secondary outcomes improved more with SMT plus HEA at 12 weeks, but only global improvement, satisfaction, and medication use had sustained improvements at 52 weeks. No serious treatment-related adverse events or deaths occurred.
The authors conclude that, for patients with BRLP, SMT plus HEA was more effective than HEA alone after 12 weeks, but the benefit was sustained only for some secondary outcomes at 52 weeks.
This is yet another pragmatic trial following the notorious and increasingly popular A+B versus B design. As pointed out repeatedly on this blog, this study design can hardly ever generate a negative result (A+B is always more than B, unless A has a negative value [which even placebos don’t have]). Thus it is not a true test of the experimental treatment but all an exercise to create a positive finding for a potentially useless treatment. Had the investigators used any mildly pleasant placebo with SMT, the result would have been the same. In this way, they could create results showing that getting a £10 cheque or meeting with pleasant company every other day, together with HEA, is more effective than HEA alone. The conclusion that the SMT, the cheque or the company have specific effects is as implicit in this article as it is potentially wrong.
The authors claim that their study was limited because patient-blinding was not possible. This is not entirely true, I think; it was limited mostly because it failed to point out that the observed outcomes could be and most likely are due to a whole range of factors which are not directly related to SMT and, most crucially, because its write-up, particularly the conclusions, wrongly implied cause and effect between SMT and the outcome. A more accurate conclusion could have been as follows: SMT plus HEA was more effective than HEA alone after 12 weeks, but the benefit was sustained only for some secondary outcomes at 52 weeks. Because the trial design did not control for non-specific effects, the observed outcomes are consistent with SMT being an impressive placebo.
No such critical thought can be found in the article; on the contrary, the authors claim in their discussion section that the current trial adds to the much-needed evidence base about SMT for subacute and chronic BRLP. Such phraseology is designed to mislead decision makers and get SMT accepted as a treatment of conditions for which it is not necessarily useful.
Research where the result is known before the study has even started (studies with a A+B versus B design) is not just useless, it is, in my view, unethical: it fails to answer a real question and is merely a waste of resources as well as an abuse of patients willingness to participate in clinical trials. But the authors of this new trial are in good and numerous company: in the realm of alternative medicine, such pseudo-research is currently being published almost on a daily basis. What is relatively new, however, that even some of the top journals are beginning to fall victim to this incessant stream of nonsense.
Many experts are critical about the current craze for dietary supplements. Now a publication suggests that it is something that can save millions.
This article examines evidence suggesting that the use of selected dietary supplements can reduce overall disease treatment-related hospital utilization costs associated with coronary heart disease (CHD) in the United States among those at a high risk of experiencing a costly, disease-related event.
Results show that:
- the potential avoided hospital utilization costs related to the use of omega-3 supplements at preventive intake levels among the target population can be as much as $2.06 billion on average per year from 2013 to 2020. The potential net savings in avoided CHD-related hospital utilization costs after accounting for the cost of omega-3 dietary supplements at preventive daily intake levels would be more than $3.88 billion in cumulative health care cost savings from 2013 to 2020.
- the use of folic acid, B6, and B12 among the target population at preventive intake levels could yield avoided CHD-related hospital utilization costs savings of an average savings of $1.52 billion per year from 2013 to 2020. The potential net savings in avoided CHD-related health care costs after accounting for the cost of folic acid, B6, and B12 utilization at preventive daily intake levels would be more than $5.23 billion in cumulative health care cost net savings during the same period.
The authors conclude that targeted dietary supplement regimens are recommended as a means to help control rising societal health care costs, and as a means for high-risk individuals to minimize the chance of having to deal with potentially costly events and to invest in increased quality of life.
These conclusions read like a ‘carte blanche’ for marketing all sorts of useless supplements to gullible consumers. I think we should take them with more than a pinch of salt.
To generate results of this nature, it is necessary to make a number of assumptions. If the assumptions are wrong, so will be the results. Furthermore, we should consider that the choice of supplements included was extremely limited and highly selected. Finally, we need to stress that the analysis related to a very specific patient group and not to the population at large. In view of these facts, caution might be advised in taking this analysis as being generalizable.
Because of these caveats, my conclusion would have been quite different: provided that the assumptions underlying these analyses are correct, the use of a small selection of dietary supplements by patients at risk of CHD might reduce health care cost.
Most of the underlying assumptions of alternative medicine (AM) lack plausibility. Whenever this is the case, so the argument put forward by an international team of researchers in a recent paper, there are difficulties involved in obtaining a valid statistical significance in clinical studies.
Using a mostly statistical approach, they argue that, since the prior probability of a research hypothesis is directly related to its scientific plausibility, the commonly used frequentist statistics, which do not account for this probability, are unsuitable for studies exploring matters in various degree disconnected from science. Any statistical significance obtained in this field should be considered with great caution and may be better applied to more plausible hypotheses (like placebo effect) than the specific efficacy of the intervention.
The researchers conclude that, since achieving meaningful statistical significance is an essential step in the validation of medical interventions, AM practices, producing only outcomes inherently resistant to statistical validation, appear not to belong to modern evidence-based medicine.
To emphasize their arguments, the researchers make the following additional points:
- It is often forgotten that frequentist statistics, commonly used in clinical trials, provides only indirect evidence in support of the hypothesis examined.
- The p-value inherently tends to exaggerate the support for the hypothesis tested, especially if the scientific plausibility of the hypothesis is low.
- When the rationale for a clinical intervention is disconnected from the basic principles of science, as in case of complementary alternative medicines, any positive result obtained in clinical studies is more reasonably ascribable to hypotheses (generally to placebo effect) other than the hypothesis on trial, which commonly is the specific efficacy of the intervention.
- Since meaningful statistical significance as a rule is an essential step to validation of a medical intervention, complementary alternative medicine cannot be considered evidence-based.
Further explanations can be found in the discussion of the article where the authors argue that the quality of the hypothesis tested should be consistent with sound logic and science and therefore have a reasonable prior probability of being correct. As a rule of thumb, assuming a “neutral” attitude towards the null hypothesis (odds = 1:1), a p-value of 0.01 or, better, 0.001 should suffice to give a satisfactory posterior probability of 0.035 and 0.005 respectively.
In the area of AM, hypotheses often are entirely inconsistent with logic and frequently fly in the face of science. Four examples can demonstrate this instantly and sufficiently, I think:
- Homeopathic remedies which contain not a single ‘active’ molecule are not likely to generate biological effects.
- Healing ‘energy’ of Reiki masters has no basis in science.
- Meridians of acupuncture are pure imagination.
- Chiropractic subluxation have never been shown to exist.
Positive results from clinical trials of implausible forms of AM are thus either due to chance, bias or must be attributed to more credible causes such as the placebo effect. Since the achievement of meaningful statistical significance is an essential step in the validation of medical interventions, unless some authentic scientific support to AM is provided, one has to conclude that AM cannot be considered as evidence-based.
Such arguments are by no means new; they have been voiced over and over again. Essentially, they amount to the old adage: IF YOU CLAIM THAT YOU HAVE A CAT IN YOUR GARDEN, A SIMPLE PICTURE MAY SUFFICE. IF YOU CLAIM THERE IS A UNICORN IN YOUR GARDEN, YOU NEED SOMETHING MORE CONVINCING. An extraordinary claim requires an extraordinary proof! Put into the context of the current discussion about AM, this means that the usual level of clinical evidence is likely to be very misleading as long as it totally neglects the biological plausibility of the prior hypothesis.
Proponents of AM do not like to hear such arguments. They usually insist on what we might call a ‘level playing field’ and fail to see why their assumptions require not only a higher level of evidence but also a reasonable scientific hypothesis. They forget that the playing field is not even to start with; to understand the situation better, they should read this excellent article. Perhaps its elegant statistical approach will convince them – but I would not hold my breath.
Medical treatments with no direct effect, such as homeopathy, are surprisingly popular. But how does a good reputation of such treatments spread and persist? Researchers from the Centre for the Study of Cultural Evolution in Stockholm believe that they have identified the mechanism.
They argue that most medical treatments result in a range of outcomes: some people improve while others deteriorate. If the people who improve are more inclined to tell others about their experiences than the people who deteriorate, ineffective or even harmful treatments would maintain a good reputation.
They conducted a fascinating study to test the hypothesis that positive outcomes are overrepresented in online medical product reviews, examined if this reputational distortion is large enough to bias people’s decisions, and explored the implications of this bias for the cultural evolution of medical treatments.
The researchers compared outcomes of weight loss treatments and fertility treatments as evidenced in clinical trials to outcomes reported in 1901 reviews on Amazon. Subsequently, in a series of experiments, they evaluated people’s choice of weight loss diet after reading different reviews. Finally, a mathematical model was used to examine if this bias could result in less effective treatments having a better reputation than more effective treatments.
The results of these investigations confirmed the hypothesis that people with better outcomes are more inclined to write reviews. After 6 months on the diet, 93% of online reviewers reported a weight loss of 10 kg or more, while just 27% of clinical trial participants experienced this level of weight change. A similar positive distortion was found in fertility treatment reviews. In a series of experiments, the researchers demonstrated that people are more inclined to begin a diet that was backed by many positive reviews, than a diet with reviews that are representative of the diet’s true effect. A mathematical model of medical cultural evolution suggested that the size of the positive distortion critically depends on the shape of the outcome distribution.
The authors concluded that online reviews overestimate the benefits of medical treatments, probably because people with negative outcomes are less inclined to tell others about their experiences. This bias can enable ineffective medical treatments to maintain a good reputation.
To me, this seems eminently plausible; but there are, of course, other reasons why bogus treatments survive or even thrive – and they may vary in their importance to the overall effect from treatment to treatment. As so often in health care, things are complex and there are multiple factors that contribute to a phenomenon.