Objective: This review examines herbs commonly used for psychiatric symptoms-St. John's wort, kava, ginkgo biloba, and valerian.
Methods: MEDLINE was searched for articles related to the use of herbs in psychiatry published after 1990. A secondary search examined sources cited in articles obtained from the MEDLINE search.
Results: Of nine controlled and standardized trials of St. John's wort, five showed the herb's superiority to placebo, and four found no differences in effectiveness when compared with antidepressant drugs. The pharmacologically active components are not known. Several double-blind, placebo-controlled trials have demonstrated the anxiolytic efficacy of kava, but these studies had ill-defined patient populations, small sample sizes, and short treatment duration. All but one of 40 controlled trials of ginkgo extracts in the treatment of dementia found clinically significant improvement in memory loss, concentration, fatigue, anxiety, and depressed mood. Most studies of gingko had poorly defined patient populations and small sample sizes and used nonstandard measures. A recent well-designed multicenter study showed significantly less decline in cognitive function among patients with dementia receiving gingko. Valerian has been shown to decrease sleep latency and nocturnal awakenings and improve subjective sleep quality, but placebo effects were marked in some studies, and in some cases the beneficial effects were not seen until two to four weeks of therapy.
Conclusions: Although evidence of the efficacy of herbal preparations in treating psychiatric conditions is growing, translating the results of efficacy studies into effective treatments for patients is hampered by the chemical complexity of the products, the lack of standardization of commonly available preparations, and the paucity of well-controlled studies.