An enthusiast of homeopathy recently posted an overview of systematic reviews of homeopathy concluding that the data we do have point towards homeopathy as having an effect greater than that of placebo:
In recent decades, homeopathy has been examined via a number of clinical trials, the number of which now allow meta-analysis. As we can see from the study findings, the type of homeopathy research (ie, individualized vs non-individualized, placebo-controlled vs non-placebo-controlled) can have a strong influence on the results, although trial quality also has a strong effect.
All meta-analyses performed in at least a somewhat open and rigorous manner have found statistically significant effects. This suggests that homeopathy has a greater-than-placebo effect, or at least a strong trend in that direction, when using data from the totality of homeopathy research, or from individualized, placebo-controlled trials. The meta-analyses with questionable methodology, one of which is undergoing government investigation for academic irregularities, have produced negative results, which have been demonstrated to be a direct result of their exclusion of vast swathes of the homeopathic clinical trial literature (based on arbitrary and unexplained criteria), as well as of their failure to differentiate – as Mathie has done – different types of homeopathic research.
The clinical data are flawed. Issues with methodology used in homeopathy RCTs, combined with a lack of research funding, have produced a lack of high-quality trials and data. However, the data we do have point towards homeopathy as having an effect greater than that of placebo.
There can be no argument with this conclusion, aside from possible new data emerging. Anyone who disputes this is going against the existing set of the highest-quality evidence on homeopathy.
His overview is based on the following publications:
|Kleijnen, 19911||All types of homeopathy (eg, single remedy vs combination). Methodological quality assessed; 105 trials. Results: Positive trend, regardless of type of homeopathy; 81 trials were positive, 24 showed no effect.|
|Linde, 19972||All types of homeopathy. Out of 185 trials, 119 met inclusion criteria; 89 of these had extractable data. Results: OR = 2.45 (95% CI 2.05-2.93).|
|Ernst, 19983||Individualized homeopathy; 5 trials determined to be high-quality. Results: OR = 0.|
|Linde, 19985||Individualized homeopathy; 32 trials, 19 of which had extractable data. Results: OR = 1.62 for all trials (95% CI 1.17-2.23). Only high-quality trials produced no significant trend.|
|Cucherat, 20009||All types of homeopathy; 118 trials, 16 of which met inclusion criteria. Used unusual method of combining p values. Results: All trials = p< 0.000036. Less than 10% dropouts: p<0.084; less than 5% dropouts (higher standards than most trials considered reliable): p<0.08 (non-significant).|
|Shang, 200511||All types of homeopathy; only 8 trials selected from 21 high-quality trials of 110 selected with unusual criteria. Results: OR = 0.88 (0.65-1.19). Result strongly disputed by statisticians.|
|Mathie, 201413||Individualized homeopathy; of the analysis pooled data from 22 higher-quality, individualized, double-blind RCTs. Results: OR = 1.53 (1.22-1.91) for all trials pooled; OR = 1.93 (1.16-3.38) for the 3 reliable trials.|
|NHMRC, 201516||Out of 176 studies, 171 were excluded, leaving only 5 for the study. Investigators used unprecedented methods, did not combine data, and are currently under investigation for outcome shopping. Results: Negative results.|
|Mathie, 201720||Non-individualized homeopathy; very few higher-quality trials. Results: For 54 trials with extractable data, SMD = -0.33 (-0.44, -0.21). When these were adjusted for publication bias, SMD = -0.16 (-0.46,-0.09). The 3 high-quality trials had non-significant results: SMD = -0.18 (-0.46, +0.09).|
|Mathie, 201821||Individualized, other-than-placebo-controlled trials; 11 trials found, 8 with extractable data. Results: 4 heterogeneous comparative trials showed a non-significant difference. One trial in this group was positive. Three heterogeneous trials with additive homeopathy showed a statistically significant SMD. No definitive conclusion possible due to trial heterogeneity, poor quality, and low number of trials.|
|Mathie, 201922||Non-individualized, other-than-placebo-controlled trials; 17 RCTs found, 14 with high risk of bias. Results: Significant heterogeneity prevented much comparison; 3 comparable trials showed a non-significant SMD.|
- Many older systematic reviews were omitted (including about 10 of my own papers). This is relevant because the author of the above review went beck until 1991 to find the reviews he included.
- Several new papers were missing as well. This is relevant because the author evidently included reviews up to 2019. Here are the key passages from the conclusions of some of them:
We tested whether p-curve accurately rejects the evidential value of significant results obtained in placebo-controlled clinical trials of homeopathic ultramolecular dilutions. Our results suggest that p-curve can accurately detect when sets of statistically significant results lack evidential value.
I am, of course, not saying that this overview amounts to anything like a systematic review. It merely gives you a flavour how trustworthy proponents of homeopathy are when they pretend to provide us with an objective evaluation of the best available evidence.