There are a number of vitamins, herbs, supplements, etc., that claim to help with depression. 5HTP, St. John's Wort, B6, etc. There is a lot of conflicting info out there and everyone's different.
I've noted a few supplements I have for moods have 5HTP, so maybe there is some value in it. I have a nutritionist/Dr. whom treats me for hypothyroid, and the accompanying or maybe, co-existing, depression. He put me on something called NeuroReplete and claimed that it should help.