Hi there.
This is really a reponse to Forward Slip & meirionydd.
Totally unqualified advice coming up here, but I researched natural supplements for my mild anxiety/mood swings several years ago since I did not want to see an "official," as I didn't deem it serious enough and feared being branded in my Govt. job(I wasn't flying btw).
This advice worked wonderfully for me, so could work for your friend.
With regard to taking St. john's Wort, can I recommend it is tried as part of a tea. It is available in herbal food shops or on the internet.
Bear in mind that the 'over the counter' pills & tablets of St. John's Wort are usually produced with a standardised extract of hypericin, the active ingredient, without the other substances in the herb, ie. you're not getting the whole plant.
There remains the question whether it is this one ingredient that makes the remedy work, or the interaction of all the ingredients of the plant that work. Something to bear in mind. From my experience, I found no effect with the tablets, yet the tea made a noticable difference.
Maybe your friend would consider seeing a herbalist? Whatever he/she decides, ensure he/she speaks to his/her doctor and informs them of their intentions.
Also, maybe take a look at an amino acid "SAMe (S-adenoslmethionine)" - expensive, but effective for depression/anxiety.
Another amino acid "L-tryptophan" - similar to 5Htp, but works better for some.
"L-theanine" - can be very calming.
As with all amino acids, you should take them with a vitamin B complex to enhance absorption.
Hope this helps.