What St. John's wort is: St. John’s wort (Hypericum perforatum) is a yellow flowering weed that has been used to treat various “nervous disorders” for centuries. It is sold in Germany, usually by prescription, as an antidepressant and in the United States as a dietary supplement. This herb contains at least seven groups of compounds that can have pharmacological action.
Claims, purported benefits: Alleviates depression, anxiety, sleep disorders, irritable bowel syndrome, hot flashes, and premenstrual syndrome (PMS). Helps with smoking cessation.
What the studies show: St. John’s wort is one of the most researched herbal medicines, in particular for its use in depression. But results have often been inconsistent and hard to compare, largely because the studies have included people with different types and degrees of depression, used different herb preparations and doses, tested the herb against low doses of antidepressants and/or did not have placebo groups.
Still, most studies have been favorable, and the consensus is that St. John’s wort works better than a placebo in treating people with mild to moderate depression, at least in the short term. It also seems to be as good as older-generation tricyclic antidepressants and, possibly, newer antidepressants for people with this level of depression, with fewer serious side effects.
The Natural Standard, which evaluates complementary and alternative therapies, has deemed the evidence convincing for St. John’s wort as a treatment for mild to moderate depression. St. John’s wort may raise levels of mood-enhancing chemicals in the brain (serotonin, dopamine and norepinephrine), which is similar to the way SSRI antidepressants work. Which constituents in the plant’s leaves and flowers may be responsible for its antidepressant action is not clear.
A well-designed study published in Menopause in 2010 found that St. John’s wort decreased hot flashes after eight weeks, but some other studies have shown no such benefit from the herb.
What it doesn’t help: Studies do not support the use of St. John’s wort for severe depression, depression of long duration, or bipolar disorder. There’s little or no good evidence that it relieves anxiety, obsessive-compulsive disorder, seasonal affective or sleep disorders or premenstrual syndrome.
It may also not help with minor depression. For instance, a well-designed 2011 study in the Journal of Psychiatric Research found that St. John’s wort worked no better than a placebo in people with minor depression over a 12-week period, but had more adverse effects.
People with irritable bowel syndrome (IBS) are often prescribed antidepressants, but they sometimes turn to alternative medicine instead, including St. John’s wort. In 2010, however, a well-designed study from the Mayo Clinic found that St. John’s wort worked no better than a placebo in relieving IBS symptoms. In fact, the placebo worked better.
Studies on St. John’s wort for smoking cessation have had conflicting results. The most recent one, from the Mayo Clinic in 2010, found that the herb, given in two different dosages, worked no better than a placebo.
The long-term safety and effectiveness of St. John’s wort are not known. Most studies have been short—less than three months. Moreover, it is not clear what the best dosage is. Although 900 milligrams a day (standardized to contain 0.3 percent hypericin and split in three doses) is commonly recommended, studies have used a range of preparations and dosages. St. John’s wort supplements vary in preparation and quality, and they may not all have the same effects as those used in studies. In 2010, testing by ConsumerLab.com found that about half of St. John’s wort supplements were contaminated with cadmium or lead and/or contained much less active ingredient than claimed. In a 2013 follow-up, however, 9 out of 10 brands passed the test.
Side effects: St. John’s wort is generally better tolerated than prescription antidepressants, but mild side effects include gastrointestinal upset, headaches, fatigue and dry mouth. It may cause increased sun sensitivity when taken at high doses or with sunsensitizing drugs.
More important, it can interfere with a variety of drugs: statins, the blood thinner warfarin (Coumadin), certain HIV medications, digoxin (a heart drug), cyclosporine (typically used by transplant recipients) and oral contraceptives, among others. Because of these potentially dangerous interactions, in 2013 a pharmacists’ group asked the Food and Drug Administration (FDA) to restrict sale of the supplement to behind the pharmacy counter.
St. John’s wort should be used cautiously, if at all, in people with bipolar or other psychiatric conditions. It may interact with other antidepressants and psychoactive medications. For instance, a 2011 study in the Journal of Clinical Pharmacy and Therapeutics showed that St. John’s wort greatly reduces blood levels of zolpidem (brand name Ambien), though this effect varied widely among the subjects.
A 2009 study in Current Eye Research found a 60 percent increased risk of self-reported cataracts in people taking St. John’s wort, after adjusting for potential confounding factors. More research is needed to confirm this, however.
Bottom line: If your depression is interfering with your life, talk to your doctor or a therapist. Depression is a serious condition, and you should not self-diagnose or self-medicate. Talk therapy is often a good option. While there is continuing debate about how effective prescription antidepressants really are, beyond their powerful placebo effect, these drugs are still often a first-choice treatment, especially for more severe depression. St. John’s wort may be an option for mild to moderate depression, but keep in mind that research on it has produced mixed results and that there is considerable variation in commercially available supplements.
If you are already taking a prescription antidepressant, don’t switch to St. John’s wort on your own. And don’t combine the two. Beware of drug interactions. Pregnant and nursing women should not take St. John’s wort.