Hi Charlie, I don't visit this site too often anymore but saw your post and I can offer you a success story. I suffered from severe depression from the ages 14 until about 22, which included symptoms identical to those you've articulated and culminated in a suicide attempt. My diet certainly changed afterwards, but I can't attribute my recovery entirely to diet. The things that most helped me include:
1. Eating less processed food, then eventually more raw food, and finally focusing on getting raw fats with a proper balance of Omega 3 and Omega 6 (i.e. about 1:1)
2. Reducing my exposure to environmental toxins, including cigarette smoke
3. Getting sun over my entire body (you need to be eating lots of good fat for this to help, otherwise your body can't turn the sun into vitamin D)
4. Spending quiet time in nature (Jon Young calls this a 'Sit Spot')
5. Learning and using the communication process called Non-Violent Communication (I started this practice about the time I started eating more raw foods, which was in 2003).
6. Talking to people about particular things that bothered me in my life (NVC was a pre-requisite for this in my case; at first I couldn't bear the thought of talking to people, so I started by talking to trees and rocks while at my sit spot and eventually reached a point where I could talk to people)
7. Became more active (yoga, martial arts, hiking; although I don't do yoga anymore, just martial arts, lots of low-intensity workouts including long walks and brief high-intensity workouts about once every 7 days)
If you want more details, let me know. Feel free to send a PM if you'd prefer that option.