I felt the book Instinct to Heal by Dr. David Servan-Schreiber:
http://www.instincttoheal.org/ covered this topic pretty comprehensively from a scientific perspective. I can't quote his recommendations because I loaned the book to a friend, but I was taking 2-3 teaspoons a day of Carlsons liquid Omega-3 fish oils (without vitamin A & D) and noticed improvement (reduction in negative attitudes about myself, less irritability) in about 5-10 days. The book (one chapter dedicated to Omega-3s and depression) had a lot of discussion of the EPA to DHA ratios and the impact that other fat soluble vitamins can have on Omega-3 interactions in the brain and body as well as discussion of Omega-6 fatty acids.
At 3 teaspoons a day, I felt ill (reflux/heartburn) and stopped taking the fish oil for a month or more. I'm definitely seeing high levels of self-criticism creeping back in and have started taking it at a lower dose (2 teaspoons) today. I was diagnosed with PTSD 1.5 years ago and severe depression about 1 year ago. Metrically, the PTSD has improved dramatically and the depression somewhat. I use a blend of treatment strategies, but very little prescription-pharmacological in the beginning and none now.