St. John's wort is an herbal treatment that's long been used for conditions including depression.
The report also warns that St. John's wort may interact with other drugs and that the quality of St. John's wort products may vary. Because of potential drug interactions, doctors need to know (and should ask) if their patients are taking St. John's wort, say the researchers.
The report doesn't totally dismiss St. John's wort. The researchers say the current evidence is "inconsistent and confusing" and say more studies should be done to clarify what benefits, if any, the herbal treatment has for depression.
The researchers, who included Klaus Linde of the Centre for Complementary Medicine Research in Munich, Germany, didn't conduct a new experiment. Instead, they reviewed 37 studies comparing St. John's wort to a placebo or standard antidepressant drugs.
In the studies reviewed, St. John's wort was shown to be barely better than placebo in treating depression. The results were better in studies not restricted to people with major depression.
Other studies showed that St. John's wort appeared to have "similar beneficial effects" as standard antidepressants, say the researchers, some of whom have received travel expenses or speaker's fees from a maker of St. John's wort products.
However, when they looked at six large, recent, more precise trials that only included people with major depression, the researchers say they found "only minimal benefits" compared with placebo.
They also say the studies showed fewer adverse effects with St. John's wort than with older antidepressants such as the tricyclic drugs. St. John's wort may also have had slightly fewer adverse effects than newer antidepressant drugs called selective serotonin reuptake inhibitors (SSRIs).
Side effects were gauged by the number of people who quit the studies because of side effects.
Here's what the National Center on Complementary and Alternative Medicine (NCCAM) says about St. John's wort:
"There is some scientific evidence that St. John's wort is useful for treating mild to moderate depression. However, recent studies suggest that St. John's wort is of no benefit in treating major depression of moderate severity," says the NCCAM's web site.
The NCCAM is a branch of the National Institutes of Health.
Quality May Vary
The quality of St. John's wort products may vary, say Linde and colleagues.
"We recommend avoiding products that do not provide important information on the content, such as the amount of total extract (e.g. 900 mg), the extraction fluid (e.g. methanol 80% or ethanol 60%), and the ratio of raw material to extract (e.g. 3-6:1)," they write.
Possible Drug Interactions
The review also reminds people that St. John's wort can interact with other drugs. Doctors should "regularly ask" their patients if they're taking St. John's wort, says the review.
It's best to tell your doctor about any herbal products, vitamins, or other treatments you're taking. That way, he or she can watch out for any interactions between treatments. Depression Is Treatable
Every year, nearly 19 million U.S. adults have a depressive illness; that's 9.5% of the population, says the National Institute of Mental Health. Depression can damage physical health while plaguing the mind and emotions.
However, it's a treatable condition. Methods include counseling, medication, and lifestyle change. Asking for help is the first step, so reach out if you suspect depression.