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See Inside Scientific American Mind Volume 24, Issue 3

Can Herbs Ease Anxiety and Depression?

Some plant-based remedies may stand in for conventional ones, but most lack scientific support as treatments for psychological problems

Scientists have studied other herbal remedies for anxiety, too. A few studies hint, for example, that lemon balm and valerian may be calming. Still, the evidence supporting their efficacy is even more preliminary than that for kava. And their potential dangers are equally uncertain.

Weeding Out Despair

St. John's wort (Hypericum perforatum), a plant historically used to drive out evil spirits, is the most widely studied herbal medicine for depression. In a 2009 review physician Klaus Linde of the Munich Technical University and his colleagues evaluated 29 well-designed studies of St. John's wort, usually taken as a pill for major depression. Overall, the studies suggested that the herb was more effective than a placebo and just as effective as antidepressants such as Prozac yet came with fewer side effects.

Not all of the studies Linde's team analyzed, however, found an advantage for St. John's wort over a placebo. In addition, two large-scale U.S. investigations revealed scant support for the idea that St. John's wort could ease depression. One of these, a 2011 study led by psychiatrist Mark H. Rapaport, then at Cedars-Sinai Hospital in Los Angeles, indicated that the plant was no more effective than a placebo for mild to moderate depression. Thus, this herb may ease some cases of depression, but the evidence is far from overwhelming.

St. John's wort is not without some risks. It can cause stomach upset, skin rashes, fatigue, restlessness, headache and confusion. More serious is the possibility, though slight, that it can interfere with becoming pregnant, worsen dementia or trigger psychosis in vulnerable individuals. And as with traditional antidepressants, St. John's wort can trigger a manic episode in people with bipolar disorder. The herb also may interact dangerously with other drugs. If taken with certain antidepressants, it may cause potentially life-threatening increases in the neurotransmitter serotonin. It also can reduce the effectiveness of birth-control pills, heart medications and HIV treatments, among other drugs.

Approved drugs for anxiety and depression carry risks, too, but in those cases, the FDA is supposed to monitor and publicize them. In contrast, no government agency regulates herbal treatments. In addition, the fact that doctors do not prescribe herbs—and often do not even know their patients are using them—raises the risk of drug interactions. Further, relatively little is known about the purity or long-term effects of herbal remedies or what dose is optimal for a particular ailment.

Despite these concerns, advertisements for herbal remedies often make exaggerated and unsubstantiated claims. One online ad for an antianxiety pill called Seredyn containing a combination of largely untested herbs asserts that “over 93% of Seredyn users with occasional anxiety and 85% with chronic anxiety report positive results, and 80–83% of users with panic and anxiety attacks say that Seredyn helps prevent and stop their attacks.” Such testimonials are essentially meaningless if not backed by verifiable data.

Nevertheless, more safe and effective herbal treatments for anxiety and depression may still be in our future. Perhaps one day scientists will discover in nature a large medicine cabinet offering new remedies for a broad spectrum of mental disorders.

(Further Reading)

St John's Wort for Major Depression. Klaus Linde, Michael M. Berner and Levente Kriston in Cochrane Library. Published online October 7, 2009.

Kava Extract versus Placebo for Treating Anxiety. Max H. Pittler and Edzard Ernst in Cochrane Library. Published online June 16, 2010.

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