St. John’s wort is an herb that has been used for centuries for treating depression and other health problems. Its effects are similar to those of prescription antidepressants, but scientific studies have not shown conclusively that it is effective.
St. John’s wort (scientific name Hypericum perforatum) is widely prescribed for depression in Europe. It appears to increase levels of the neurotransmitters (nerve messengers) serotonin and dopamine, substances that are targeted by prescription antidepressants. However, evidence regarding its effectiveness in treating depression has been mixed. A systematic review of 29 international studies published in 2009 suggests that St. John’s wort may be superior to placebo (an inactive substance) and equally effective as prescription antidepressants at treating mild-to-moderate depression. These studies were conducted in Europe, where St. John’s wort has long been used in the medical community. Yet other studies conducted in the United States have found that St. John’s wort was no more effective than placebo.
St. John’s wort may have a number of side effects and may interact with other drugs. Combining it with antidepressants that increase serotonin levels, such as selective serotonin reuptake inhibitors (SSRIs), may lead to serotonin syndrome. This condition is characterized by a dangerous increase in serotonin levels, which may lead to tremor, diarrhea, confusion, and death. St. John’s wort may also interfere with and weaken the effects of certain prescription drugs, such as antidepressants and birth control pills.
The National Center for Complementary and Alternative Medicine (NCCAM), a branch of the National Institutes of Health (NIH), recommends against using St. John’s wort in place of standard medical care for depression. NCCAM recommends letting your health-care providers know about any complementary health approaches you use, including St. John’s wort.