Last time I discussed the problem of missing evidence of harm in homeopathy trials and consequently in systematic reviews. This time, I’m going to discuss some evidence of harm that we DO have. Sadly, it’s not comforting.
In December 2012, a systematic review of the adverse effects of homeopathy was published in the International Journal of Clinical Practice (aside: for a quick explanation of systematic reviews and adverse effects, take a look at volume 2 in this blog series). The authors of this review searched five databases of medical literature totalling nearly 50 million published trials (though likely with considerable overlap), and found just 38 articles that discussed case reports and case series of adverse events with homeopathy.
It’s worth noting at this point that if systematic reviews are the pinnacle of the evidence pyramid, case reports and case series are somewhere towards the middle or bottom, depending who you ask. They’re not ideal, because they’re not rigorous – they rely on someone not only noticing an adverse event and linking it to homeopathy, but taking the time to sit down and write about it and submit it to a journal. Then of course they’ve got to find a journal willing to publish it. If any of these steps don’t happen, there’s no published evidence for the rest of us to base our decisions on. So if our systematic review found 38 published reports, the obvious question is “how many were never recognised, written up, or published?” We’ll never know the answer to that. Sadly in the absence of high quality reports of harm from the published clinical trials, this is the highest level of evidence we have.
Back to the review. The 38 retrieved reports contained information relating to 1,159 people from all over the world. Surprisingly, only 17 of the reports related to indirect harms – the results of substituting conventional care with homeopathy – although some of those indirect harms were severe. Several people were admitted to hospital (including intensive care) due to replacing their conventional medicines with homeopathy, at least one was left with permanent effects, and one person died.
That leaves 1,142 people who suffered *direct* adverse effects as a result of using homeopathy. This seems rather counter-intuitive, and I’m at a loss to explain to explain many of them given that your average homeopathic remedy contains precisely no active ingredient. The authors of the review suggest that perhaps allergic reactions or ingestion of toxic metals (like arsenic or mercury) might be partly to blame. They also suggest that low dilutions of remedies might be a potential source of adverse effects, but point out that the vast majority of these reports were associated with remedies at 12C potency or below. To be clear, 12C is the dilution factor at which the chance of a remedy containing even one molecule of the original parent substance is effectively zero.
But whatever the mechanism, it seems clear that the review provides evidence of direct harm being caused by homeopathy. Some of these harms were reported simply as “mild”, with no other details offered. Some were potentially very distressing, like dermatitis, hair loss, and migraine. Some were very serious indeed, including anaphylaxis (life-threatening allergy), acute pancreatitis, cancers, and coma. Once again the consequences of the effects included hospitalisation, admission to intensive care units, and death. For a treatment modality generally touted as totally safe, that’s a pretty alarming set of side effects.
So what can we learn from it? There’s a valid argument to be made that there’s little point conducting more randomised controlled trials of homeopathy, because all of the good quality ones end up showing the same thing: no benefit over placebo. But where more trials are conducted, we should be demanding that all adverse effects are collected and reported in the same manner as trials of new medicines. Case series and reports are not proof of causation, but there is a bulk of evidence here that is concerning, and which should be addressed. The best way to do that is in good quality trials.
In the mean time, is there anything else we can do? Yes there is – in the UK at least. The medicines regulator in the UK, the MHRA, runs the Yellow Card Scheme. This is a mechanism by which anyone can report any side effect they experience after taking a medication. I would strongly urge anyone who has suffered an adverse event after using homeopathy (or who knows someone who has) to visit www.mhra.gov.uk/yellowcard. It’s quick and simple, and will help make remedies safer for everyone. Similar schemes will be coming into effect throughout the EU soon, but if you live elsewhere please check and see if there’s anything similar. We need all the data we can get!