The Homeopathy Research Institute (HRI) is a UK-based organization, dedicated to generating and communicating high-quality research in homeopathy at an international level. HRI also aims to promote fairness and objectivity in how the evidence for homeopathy is used and evaluated, especially by those who are new to this specialist field. Our biennial research conferences play a key role in achieving these aims.

In June 2023, HRI held its fifth conference on the theme: ‘Cutting Edge Research in Homeopathy’. Alongside our conference report[1] and abstracts,[2] this guest Editorial provides a timely opportunity to reflect on a decade of HRI conferences and ask not only, ‘How has the homeopathy research sector evolved over this period?’, but also, ‘Where is homeopathy research heading, as we look to the future?’.

Ten years ago, at the time of our inaugural conference, there were numerous claims that ‘there is no evidence’ for homeopathy and ‘it's just placebo’. The main aim of HRI Barcelona 2013 was therefore a simple one – to physically demonstrate the existence of homeopathy research; not just the evidence itself, but also the existence of an established community of researchers, affirming its legitimacy as a scientific field.[3]

Two years later, the HRI Rome 2015 conference effectively illustrated that the evidence for homeopathy was both increasing in volume and improving in quality[3]; the robust systematic review/meta-analysis of individualised homeopathy by Mathie et al had recently been published in the high impact journal ‘Systematic Reviews’, showing that ‘gold standard’ placebo-controlled double-blind randomized controlled trials (RCTs) could detect a significant difference between the effect of individualised homeopathic medicines and placebo.[4] This meta-analysis was pivotal in moving the ‘homeopathy debate’ forward – or so one could have expected, according to usual scientific processes.

The HRI Malta 2017 [3] conference took a more self-reflective stance, with presentations and discussion focusing on learning from the past, to make future studies even more robust, as the sector continued its clear commitment to building on existing positive findings. By contrast, the unspoken theme during HRI London 2019 was bolder and clear to all who attended: i.e., the direction of evidence had become strong enough for the sector to take the more categorical position that the evidence simply does not support the hypothesis that homeopathy is merely a placebo effect – despite detractors continuing to make this claim.[3]

A strong outcome from all HRI conferences has been their importance in building networks, bringing research groups together, and providing a supportive environment for the exchange of ideas. Regrettably, during the COVID pandemic the HRI conference was forced to become a virtual event, and while researchers around the world were temporarily forced to work in isolation from one another, our chosen theme for HRI Online 2022 was the tangible positive impacts resulting from international collaboration.[3] The feedback we received confirmed HRI Online 2022 to be a great success, particularly in terms of reaching new audiences who had not attended our previous European-based events due to distance. However, the limitations of the online conference model were also confirmed for the HRI team; sitting alone watching carefully worded public presentations online is no substitute for 2½ days of intensive, in-person exchange, speaking freely about truly novel work and ideas, with colleagues both old and new.

For this reason, we were delighted to hold our latest event, HRI London 2023, in person. As we re-convened after the 4-year hiatus, the sector's maturity was evident.[1] A shift in research focus was also clear, with our earlier conferences emphasizing more clinical studies, while HRI London 2023 placed more emphasis on in vitro experiments, physicochemical approaches, and fundamental research – each of them contributing, from different angles, to the exploration of mode of action of homeopathic medicines.

Despite this progression within the homeopathy research field from 2013 to 2023, over this same period the homeopathy debate has remained highly charged: HRI London 2023 was held against a backdrop of persistent refusal from many conventional scientists to accept that homeopathy is rapidly becoming an increasingly evidence-based discipline. Notably, in the lead-up to this most recent conference, Sigurdson et al[5] published a paper confirming that clinical trials do indeed show homeopathy has beneficial effects beyond placebo – but the authors still dismissed this result as ‘noise’.

In their study, Sigurdson et al[5] selected 50 placebo controlled RCTs of homeopathy and calculated the overall effect size. They found that 80% of the trials were positive for homeopathy, and that homeopathy was twice as likely to have a beneficial effect than placebo (mean effect size 0.36, Odds Ratio 1.94). This positive result is consistent with the findings of Mathie et al,[4] where individualised homeopathic treatment was 1.5- to 2-times more likely to be beneficial than placebo. But Sigurdson et al deemed these positive results to be simply an empirical estimate for the level of error due to bias found in all clinical trials.

To arrive at their position Sigurdson et al made two key assumptions:

Homeopathy is a “null field”: i.e., “a scientific field where there is nothing to discover and where observed associations are thus expected simply to reflect the magnitude of bias”.[6]

All placebo controlled RCTs of homeopathy are essentially comparing placebo versus placebo: i.e., there is no possibility that any beneficial effects seen are genuine or directly attributable to treatment.

Such flawed logic by experienced scientists clearly requires further exploration, especially as this is an opposing view to that held by experts on homeopathy research, including the 203 scientists who have, in total, provided 10 years' worth of HRI conference content.

The a priori assumption of Sigurdson et al, that homeopathic medicines cannot work and therefore must be nothing more than placebo, is itself a well-recognised and pervasive source of bias that has been documented in the literature for over 20 years.[7] This ‘plausibility bias’[8] blinds the researcher to the possibility that the beneficial effects of homeopathic medicines detected in placebo-controlled trials are real clinical effects, occurring via a non-biochemical mechanism of action that has yet to be understood.

It is therefore both ironic and deeply disappointing that a study aimed at quantifying bias is itself built entirely on a well-documented and specific type of bias. Furthermore, when one considers that homeopathic medicines have demonstrable effects, not only in humans but in multiple animal[9] and plant[10] species, as well as in molecular studies,[11] taking the stance that “homeopathy is impossible” is a purely theoretical argument that disregards the actual scientific evidence. This calls to mind a quote from futurologist and author, Arthur C. Clarke: “If an elderly but distinguished scientist says something is possible, he's very possibly right, but if he says it's impossible, he's very probably wrong”.

As the evidence for homeopathy grows, the idea that homeopathy is just a placebo effect is becoming increasingly implausible. Only time will tell how much positive evidence is required to break through the plausibility bias blinkers worn by authors such as Sigurdson et al.,[5] but in the meantime we can be in no doubt that attempts to deny the existence, quality and/or meaning of the positive scientific evidence for homeopathy will persist for some years to come.

Viewing the clinical evidence base on homeopathy objectively requires us to acknowledge its weaknesses, such as small trial sample sizes (e.g., a median of 62.5 participants),[12] heterogeneity of datasets and a limited number of primary studies per medical condition (on average approximately two trials per condition).[13] However, such limitations are nothing unusual in clinical research, being widespread in the evidence base for conventional medicine too. A recent study estimated that only 6% of eligible RCTs included in Cochrane reviews are deemed to be low risk of bias[14] and only 4–6%[15] [16] of conventional medical treatments are known to have genuine beneficial effects supported by high quality (bias free) evidence. So, while more research is clearly needed to further develop the evidence base on homeopathy, as we reflect on a decade of progress in this field, it is important to recognise that the current status of clinical research on homeopathy is now similar to that of many conventional medical treatments.

With plans for the 6th HRI conference now underway—to be held in Europe in June 2025—we are already curious as to what abstracts will be submitted by our colleagues when the time comes: will we be showcasing evidence that consolidates and strengthens what we already have, or will there be findings that make some exciting leap into as-yet uncharted territory? Either way, as we look to the future, the HRI team will be keeping the words of aviation pioneer, Amelia Earhart, in our minds: “Never interrupt someone doing what you said couldn’t be done”.

Article published online:
29 January 2024

© 2024. Faculty of Homeopathy. This article is published by Thieme.

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