Background: Homeopathic pathogenetic trials (provings) are fundamental to homeopathy. Since most of the data from available provings have not been statistically evaluated, it is unclear how specific reported symptoms are and how they differ from those reported by people taking placebo.
Method: We combine and analyse data from two different homeopathic pathogenic trials--including 10 and 11 provers, respectively, and both including 30% placebo-to test the null hypothesis that there is no significant difference between the number of symptoms in placebo and verum groups.
Results: The principal results were: Placebo reported less symptoms than verum groups. Symptom distribution according to predefined classes (common symptoms increased in intensity and/or duration-, cured, old, new and exceptional) was statistically different between placebo and verum group at a high level of significance (P<0.001). Compared to verum, placebo provers reported less new and old but more common (increased in duration or intensity) symptoms. Within repertory categories, other differences were detected. The two groups differ in terms of the duration of each symptom and kinetics of symptoms: most symptoms were more persistent in verum than in placebo groups and verum provers recorded a decreasing number of symptoms with time. Placebo provers did not show such a temporal pattern.
Conclusions: If confirmed by other studies these results would demonstrate the non-equivalence between homeopathic medicines in high dilution and placebo and contribute to the improvement of proving methodology and evaluation.