Here’s the rationale supporting this study by researchers at the Mayo Clinic, in Rochester, Minnesota.

St. John’s wort treats mild-to-moderate depression. Antidepressants are often used to treat irritable bowel syndrome (IBS). But no one has studied the effects of St. John’s wort in patients with IBS.

First, the details.

  • 70 patients with IBS were randomly assigned to take either St. John’s wort or placebo.
    • Assignment of treatment was balanced according to symptom subtype: constipation predominant IBS, diarrhea predominant IBS, or mixed IBS.
  • The primary end point was self-reported overall bowel symptom score at 12 weeks.
  • The patients and researchers were not aware of the treatment given — double blind.

And, the results.

  • Both groups reported decreases in overall self-reported bowel symptoms scores, with the placebo group having significantly lower scores at 12 weeks vs St. John’s wort.
  • The placebo group also did better than the St. John’s wort-treated patients at week 12 for diarrhea and “adequate relief.”
  • Both groups believed that the drug they received decreased IBS life interferences.

The bottom line?

St. John’s wort is less effective than placebo for treating IBS.

1/10/10 20:57 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.