What are the warnings for St. John's wort?

There are several warnings for St. John's wort:

• Do not use St. John's wort externally (on your skin). No one knows yet if applying it to the skin is safe, and doing so can make your skin extremely sensitive to sunlight.
• It is probably safe for most people to take St. John's wort orally (by mouth) for up to 8 weeks. And it seems to be safe for children under 12 to take it for up to 6 weeks. But it may be unsafe for anybody to take too much of it and unsafe for some people to take any at all.
• Large doses (such as 2 to 4 grams a day) can cause severe skin reactions to the sun. When taking St. John's wort, it's wise to wear sunscreen.
• Do not take St. John's wort if you're pregnant, breast-feeding or trying to become pregnant.
• St. John's wort may make attention-deficit/hyperactivity disorder (ADHD) symptoms worse. In particular, anyone taking methylphenidate to treat ADHD should not take St. John's wort.
• St. John's wort may induce mania (excessive physical activity and impulsive behavior) in people with major depression or bipolar disorder. In people who are bipolar, it may also accelerate the cycling between depression and mania.
• There's a danger that St. John's wort may bring on psychosis in some people with schizophrenia and may make dementia worse in people with Alzheimer's disease.
• Stop taking St. John's wort at least two weeks before surgery. Anesthesia can cause serious heart complications for people who have used St. John's wort for six months.                         
• St. John's Wort can interact with certain drugs and in some cases can cause very serious reactions. Talk to your doctor about your medications before you take St. John's wort.