Over the past three years St. John's wort has become one of the most popular
herbs due to its consistent and effective antidepressant actions. Many
Americans are starting to substitute this herb for pharmaceutical
antidepressants. But how does this herb work? Up to now we still don't exactly
know which brain chemical systems are most influenced. Researchers at the
School of Pharmacy, at Temple University in Philadelphia did a review of
published antidepressant mechanism(s) of action of St. John's wort. Although
the authors of the study are still not clear, they believe that St. John's
wort mechanism of action is similar to that of the synthetic antidepressants,
such as the selective serotonin-reuptake inhibitors (such as Prozac) or
monoamine oxidase (MAO) inhibitors. But they add that the inhibition by this
herb is weak relative to the pharmaceutical drugs and that other mechanisms
are possible.
Comments: Having reviewed the published studies with this herb, I tend to
agree that the clinical efficacy of St. John's wort is probably attributable
to the combined contribution of several mechanisms, each one too weak by
itself to account for the overall effect. This is what makes St. John's herb a
special herb. By working on several brain chemical systems, its overall
benefits are enhanced while the possible side effects are reduced.
Bennett DA Jr, Phun L, Polk JF, Voglino SA, Zlotnik V, Raffa RB.
Neuropharmacology of St. John's Wort. Ann Pharmacother 1998 Nov;32(11):1201-8