How Homeopathy is Treated in Meta-analyses

Many scientists reject homeopathy because there is no plausible mechanism of action. However, medical care today is evidence-based, where a mechanism is not crucial. With abundant literature, evidence is obtained by meta-analyses and systematic reviews. Sadly, several meta-analyses authored by classical scientists and skeptics, where homeopathic treatment is compared to placebo (water), show evidence of manipulation and bad judgment.

The story starts in 1997 when Klaus Linde and co-workers identified 89 clinical trials that showed an overall odds ratio of 2.45 in favor of homeopathy over placebo. This difference was statistically significant. Linde reported a trend toward smaller benefit from studies of the highest quality, but the 10 trials with the highest quality (highest Jadad score) still showed homeopathy had a statistically significant effect.

These results challenged academics to perform alternative analyses that, to demonstrate lack of effect, relied on extensive exclusion of studies, often to the degree that conclusions were based on only 5-10% of the material, or on virtual data. Such extensive exclusion exercises, created in retrospect, opens the way for the authors to manipulate the outcome by creating statistical Type II errors and flip-flop phenomena. The ultimate argument against homeopathy is the “funnel plot” published by Shang’s group in 2005. However, the funnel plot model is flawed when applied to a mixture of diseases, because studies with expected strong treatment effects are, for ethical reasons, powered lower than studies with expected weak or unclear treatment effects.

To conclude that homeopathy lacks clinical effect, scientists must overlook more than 90% of the available clinical trials. Alternatively, flawed statistical methods must be applied.

Keywords: Homeopathy, study quality, meta-analysis, randomized controlled trials