psisci - FYI. The 1984 study by Suzuki, Katsumata, etal, in the journal Planta Medica (1884; 50: 272-274) reported that hypericin in SJW had significant mono-amine oxidase activity, but subsequent studies suggested that impurities in the hypericin were responsible for the results. Further investigations did show that SJW did have minimal MAOI activity, but at levels far below that required for therapeutic effect (see: Upton R, editor. St. John's Wort Monograph. Santa Cruz. American Herbal Pharmacopoeia Inc., 1997: 1-32). Inhibition of serotonin reuptake activity has been suggested, but again concentrations appear to be inadequate (see Upton, 1997). Indications are that the psychotherapeutic properties of hypericum (another constituent of SJW) are due to other causes, possibly related to GABA or reduced interleukin-6 expression (see Upton, 1997), but further studies are needed.

Studies of hyperforin was identified as a major active component of hypericum extract, and is a potent inhibitor of serotonin, norepinephrine, and dopamine neuronal reuptake. Hyperforin also inhibits the synaptosomal uptake of L-glutamate and stimulates GABA receptors (see Chatterjee SS, et al. Life Sci 63; 1998: 499-510a).

That being said, the actual mechanism of action of SJW has not been definitively established. Compared to SSRIs, TCAs, and SNRIs, SJW has far less antidepressant activity, but not a more favourable side effects profile, and can interact adversely with several medications due to inhibition of the liver's Cytochrome P-450 system. SJW also can cause photosensitivty reactions, making one's skin more sensitive to sunlight.

Also, all positive clinical trials of SJW use the expensive plant extracts, which can put a good dent in one's pocketbook.

Just my two-bits. - Cam