NEW YORK (Reuters) -- An herbal remedy for depression that is extremely popular in Germany may indeed be better than a placebo at relieving depression.
However, more research is needed to determine how extracts of the plant, called St. John's wort, compares to other antidepressants, according to a report in this week's British Medical Journal.
"This works by a different mechanism than standard antidepressant drugs, so it may have something unique to offer to patients," commented Dr. Gary Sachs, assistant professor of psychiatry at Harvard Medical School in Boston. "We are always interested in having another tool in the toolbox."
Unlike other antidepressants, St. John's wort, or Hypericum perforatum, does not cross the blood-brain barrier, and therefore cannot affect the neurotransmitters in the brain thought to be involved in depression, he said. However, the plant may suppress the secretion of adrenocorticotropic hormone from the adrenal glands, which causes high blood levels of the stress hormone cortisol.
"In truth, we don't know how [hypericum] works," but chronic exposure to cortisol is thought to contribute to depression, he noted.
In 1993, 2.7 million prescriptions for the herb were written for the treatment of anxiety, depression and sleep problems in Germany, according to the report from German and American researchers.
An analysis of 23 studies of the herb found that it was twice as effective as a dummy medication at relieving depression. However, different doses and types of hypericum were used, and patients were followed for no more than eight weeks so "current evidence is inadequate to establish whether hypericum is as effective as other antidepressants," concluded lead study author Dr. Klaus Linde, of the Ludwig-Maximilians University in Munich. While the side effects -- which include stomach upset, allergic reactions and fatigue -- appear to be mild, patients have only been followed for short periods of time.
It would be "premature" to recommend the herbal remedy to patients in this country, said Sachs.
While a naturally occurring treatment may be appealing, it is not clear how hypericum interacts with other medication, what dose is safe and effective, and whether it is useful for some types of depression, but not others, according to Sachs.
"Anything that might be helpful where the risk to benefit ratio is favorable ought to be presented to patients, but I don't have a great deal of confidence that this is a reasonable choice," he said.
