I had always understood that St. Johns Wort was thought to be one of the few "alternative" remedies that actually had a degree of scientific support for its use :)
As others have already mentioned, probably a good idea to go see the GP, and as a rule taking a medication for 10 years without clinical guidance is probably not the best idea...
Interesting about herbal medicine and Germans though- Mistletoe as a treatment for cancer seems to have a following over there, despite there being little evidence and few if any clinical trials that i know of...
They are also big fans of homeopathy and anthroposophical medicine, again treatments with little clinical evidence or scientific plausibility that support their efficacy