I would highly recommend reading the book Optimum Nutrition For The Mind by Patrick Holford. It is the singularly most helpful book I have ever come across on the topic of supplements and vitamins for the mind. He has worked with top Harvard psychiatrists who are mentioned in the book. It is based on sound principles that I myself used...and it worked.
5HTP is mentioned in there, as well as Tryptophan and recommends the foods that contain it and also if you choose to supplement the quantities that are safe....As far as herbs go - Valerian was mentioned. That book was a God-send to me. Hopefully, it can assist your friend. Depression is a killer.
