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A Review of Herbal Medicines for Psychiatric Disorders

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The increasing interest in and use of herbal remedies by patients has created a need for psychiatrists and other mental health professionals to become familiar with the effects of more commonly used herbs, including their risks, side effects, and contraindications.

Unfortunately, this topic is not covered in most medical school curricula, psychiatry residency programs, or textbooks of psychiatry and psychopharmacology. However, this situation is beginning to change, as evidenced by a recent issue of JAMA devoted to alternative medicine (November 11, 1998).

Once considered a counterculture phenomenon, herbal medicines are now a $4 billion industry, and herbal products are readily available in drugstores and supermarkets. It has been estimated that one of every three Americans has used herbal remedies, with 50 million people using them in a given month. Four of the 12 most commonly used herbal medications—St. John’s wort, kava, ginkgo, and valerian—are taken for the prevention or treatment of psychiatric symptoms, which is the most rapidly growing segment of the herbal product market.

Review Objective

This review examines herbs commonly used for psychiatric symptoms—St. John’s wort, kava, ginkgo biloba, and valerian.

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.


St. John’s wort

St. John’s wort (Hypericum perforatum) is an aromatic perennial that is native to Europe but now grows wild in parts of Asia, North America, and South America. Its use can be traced back to the texts of the ancient Greek physicians Hippocrates and Galen. In the past decade it has become the second most commonly used herbal remedy in Germany and is currently used in that country for the treatment of depression four times more often than the most commonly used prescription antidepressant. In the United States, St. John’s wort is the second most commonly purchased herbal product. An estimated 17% of Americans have taken products containing St. John’s wort.

However, if the analysis is restricted to well-controlled trials using standardised dosages and standard outcome measures, nine studies are of interest (3). Five of these were placebo-controlled studies using 900 mg per day of an aqueous methanol extract referred to in the literature as LI 160, with a treatment duration of at least four weeks. The five studies (3) used the Hamilton Rating Scale for Depression (HAMD) as an outcome measure (12). Overall, patients receiving the extract showed a slightly greater improvement in HAMD scores than those receiving placebo. When response was defined as at least a 50% decline in HAMD scores, 61% of the patients receiving the extract responded, compared with 24% receiving a placebo.


The kava shrub (Piper methysticum) is native to Polynesia and the Pacific Islands, and it has traditionally been taken by Pacific Islanders as a beverage mixed with water and coconut milk. Kava is becoming a popular herbal product in the United States, with sales increasing rapidly. Most medicinal forms are either ethanol-water or acetone-water extracts.

Several double-blind, placebo-controlled trials have been conducted using a standardised extract containing 70% kavapyrones given in a dosage of 210 mg a day (3). In two of these studies, a significant difference in scores on the Hamilton Anxiety Rating Scale (HAMA) (33) was seen after only one week of treatment; in the third and largest study, a significant difference in HAMA scores was seen after eight weeks, with the difference continuing until the study terminated at week 25 (3). Several double-blind studies have also demonstrated that DL-kawain, one of the kavapyrones, in dosages of 200 to 600 mg a day is more effective than placebo as measured by reduced HAMA scores (3).


Ginkgo trees (Ginkgo biloba) are native to East Asia and are grown ornamentally in Europe and North America. Used in China for more than 2,000 years as a tea for treatment of asthma, ginkgo is now the most commonly sold herbal product in Germany and one of the top three herbals in the United States, where it is taken primarily to prevent or treat memory problems (1,3). U.S. sales increased markedly after a report in JAMA of a clinical trial of the use of kava for patients with dementia (39).

A more recent 52-week, randomised, double-blind, placebo-controlled, multicenter study of more than 300 patients with Alzheimer’s disease or vascular dementia used the EGb 761 extract at a dosage of 120 mg a day (39).

The group taking ginkgo extract showed significantly less decline on two of the three standardised rating scales. The outcome measure was improvement of 4 points or more on the cognitive subscale of the Alzheimer Disease Assessment Scale (41), which is roughly equivalent to a six-month reversal of symptoms. On the basis of this measure, 27% of the EGb group improved, compared with 14% of the placebo group. Although these effects are modest, they may be valuable to patients and families and are not unlike results from studies of cholinesterase inhibitors.

More study is clearly warranted to determine which patients might benefit from this treatment.


Approximately 250 different species of valerian exist. The one used most commonly for medicinal purposes (Valeriana officinalis) is a perennial that is native to Europe and Asia. Valerian root is frequently made into a tea by adding 3 to 5 g of dried valerian root to hot water and straining after ten to 15 minutes (4). In addition, a variety of extracts and tinctures have been prepared, with considerable differences in composition between the aqueous and ethanol extracts (3). Preparations available in the United States are often mixtures that include other ingredients such as passion flower.

Several studies of the effects of valerian extracts on sleep have been conducted. In healthy human subjects, 400 to 900 mg of valerian extract decreased sleep latency and nocturnal awakenings and improved subjective sleep quality (43,44,45). However, placebo effects were marked in some studies, and in some cases the beneficial effects of valerian were not seen until after two to four weeks of therapy.


It is becoming increasingly important for physicians to be familiar with the herbal remedies commonly used in the patient populations they serve. Our patients are frequently exposed to sketchy information about these products through the media or marketing campaigns, and they will quite rightly expect their physicians to be able to answer their questions about indications, risks, interactions, and side effects of herbal products.

In addition, increasing numbers of clients express a preference for the use of remedies they perceive to be “natural,” and physicians familiar with the available research will be better equipped to make informed and safe decisions about whether it is appropriate to recommend herbal remedies in selected cases.

Although evidence of the efficacy of certain herbal preparations in the treatment of psychiatric conditions is growing, translating the results of efficacy studies into effective treatments for patients is hampered by the chemical complexity of the products and the lack of standardisation of commonly available preparations, not to mention the paucity of well-controlled studies of safety and efficacy. In particular, well-controlled studies comparing herbal remedies with conventional medications are few. As a result, it is premature for psychiatrists to recommend herbal remedies over established conventional treatments.


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