ROCHESTER, Minn.—St John's wort was less effective for treating irritable bowel syndrome (IBS) than placebo in a recent Mayo Clinic study (Am J Gastroenterol. 2009 Oct 6. doi:10.1038/ajg.2009.577). St John's wort is known to effectively treat patients with mild-to-moderate depression, and antidepressants are frequently used to treat irritable bowel syndrome (IBS), leading to the conclusion that the botanical may treat IBS. However, no such connection was found in the 12-week study.
In this randomized, double-blind, placebo-controlled trial, 70 participants with an established diagnosis of IBS were randomized and assigned to either St John's wort or placebo. In all, 86 percent of the participants were women, and the median age was 42 years. Twenty-nine percent of the subjects suffered from constipation, 37 percent experienced diarrhea, and 31 percent had both symptoms.
At the end of the study, both groups reported decreases in overall IBS symptoms from baseline, with the placebo arm having significantly lower scores at 12 weeks (P=0.03) compared with those who took St. John's wort. These patterns of improvement were mirrored in the secondary end points with the placebo group faring better than the St John's wort-treated group, with significant differences observed at week 12 for diarrhea (P=0.03) and percent with adequate relief (P=0.02). A similar proportion of subjects in each treatment group (St John's wort: 51 percent vs. placebo: 54 percent) believed that the study drug they received decreased IBS life interferences (P=0.79).