No amount of counselling will cure depression caused by physiological factors, although it will help. I still say it's best to work with a professional to determine the cause, and try to do something about that. The cause may be mental, or it may be physical. There is no "silver bullet," "one-size-fits-all" treatment - not drugs nor counselling.

From the FDA Public Health Advisory (Feb 10, 2000) on this page"

"Based on this study and reports in the medical literature, St. John's wort appears to be an inducer of an important metabolic pathway, cytochrome P450. As many prescription drugs used to treat conditions such as heart disease, depression, seizures, certain cancers or to prevent conditions such as transplant rejection or pregnancy (oral contraceptives) are metabolized via this pathway, health care providers should alert patients about these potential drug interactions to prevent loss of therapeutic effect of any drug metabolized via the cytochrome P450 pathway."

FromSt John's wort for depression--an overview and meta-analysis of randomised clinical trials published in the British Medical Journal - BMJ 1996;313:253-258 (3 August):

"The mechanism of action of the postulated antidepressant effects is unclear."

This one's got some great information, not just on St John's Wort, but other things (ginkgo, garlic, ginsing, valerian, kava-kava, yohimbine, echinacea, feverfew, as well.):

"Crude plant extract xanthenones have demonstrated MAO inhibition in rat brain studies, but it is unclear if hypericin itself inhibits MAO-A or -B in the human nervous system."

"Supporting the biogenic amine antidepressant effect of SJW, Perovic and Müller demonstrated hypericum extract inhibition of serotonin (5-HT) uptake in rat synaptosomes."

So it appears St John's Wort may be both MAO inhibitor and serotonin uptake inhibitor.

Also, important to note for those who've tried it and given up early:

"Onset of its mood-elevating effect usually occurs after several weeks."