Effectiveness
In a 2002 database review of randomized trials Edzard Ernst concluded:
The hypothesis that flower remedies are associated with effects beyond a placebo response is not supported by data from rigorous clinical trials.
All randomized double-blind studies, whether finding for or against the remedies, have suffered from small cohort sizes but the studies using the best methodology were the ones that found no effect over placebo. The most likely means of action for flower remedies is as placebos, enhanced by introspection on the patient's emotional state, or simply being listened to by the practitioner. The act of selecting and taking a remedy may act as a calming ritual.
A systematic review in 2009 concluded:
Most of the available evidence regarding the efficacy and safety of BFRs has a high risk of bias. We conclude that, based on the reported adverse events in these six trials, BFRs are probably safe. Few controlled prospective trials of BFRs for psychological problems and pain exist. Our analysis of the four controlled trials of BFRs for examination anxiety and ADHD indicates that there is no evidence of benefit compared with a placebo intervention.
A newer systematic review published in 2010 by Ernst concluded
All placebo-controlled trials failed to demonstrate efficacy. It is concluded that the most reliable clinical trials do not show any differences between flower remedies and placebos.
Read more about this topic: Bach Flower Remedies