WARNING! If you have bipolar disorder, avoid St. John's Wort. My husband has BPD, and used st john's wort for a full year before having any side effects, and when they came, they were a DOOZY!
He said he felt like his brain was sitting on a frying pan and sizzling, and if he'd had a gun, he would have shot himself in the head, not because he was suicidal, but simply to bring an end to the sizzling sensation.
It took a year for the herb to saturate into his system enough to bring this on, but it was a VERY unhappy side effect for him. It lasted an entire afternoon, three or four hours of brain sizzle. Not something he ever wants to repeat.
