Objective: This work aimed to identify controlled trials, which evaluated effectiveness of herbal medicines in subjects suffering generalized anxiety disorder.
Method: Controlled studies (randomized, comparative with placebo and/or standard drug, double-blind) were sought through electronic and hand-searches. The word strategy used "plant OR phytomed* OR extract OR herbal OR medicinal (OR specific name plants)" e "anxie* OR anxioly* OR tranquil* OR GAD", limited to "human OR clinical trial OR randomized controlled trial OR meta-analysis OR review". The search was restricted to English language.
Results: Piper methysticum presented an unequivocal anxiolytic effect, but most studies also included patients with other anxiety disorders (e.g. phobias). Isolated studies with Ginkgo biloba, Galphimia glauca, Matricaria recutita, Passiflora incarnata and Valeriana officinalis showed a potential use for anxious diseases. Despite this low number of studies, Ginkgo biloba and Matricaria recutita showed an effect size (Cohen's d=0.47 to 0.87) similar or higher to standard anxiolytics drugs (benzodiazepines, buspirone and antidepressants-0.17 to 0.38). No additional study with other plants was found.
Conclusion: Despite the therapeutic potential of medicinal plants in generalized anxiety disorder, very few controlled trials assessing herbal medicines in generalized anxiety disorder were found. Additionally, these studies present serious flaw design.