First: sorry for my bad english, I'm not a native speaker but I wanted to tell you my experience.
A year ago, from one day to another, I got really sick with digestive problems (irritable bowel syndrome), dry eyes and dry mouth, joint pain and vitamin defieciency. So I started to change my diet completely. My doctor found that I have fructose malabsorbtion, so i stopped eating fructose. It didn't change my digestive problems, but my mood! I kept a nutrition diary and noticed, that half a day after I ate fructose, first I had a "high" followed two or three hours later with depression or suicidal feelings. Until today I couldn't fix my gut, but at least I could stop my therapy and don't have this tremendous stress anymore. I shoul say that I stopped eating sugar completely and try to cook my food on my own, eat fresh food and many vegetables.
I don't want to say that it's the solution for everyone, but perhaps it's a little hope that I can give. I really love this forum and you helped me alot to going on when I had my bad times. Thank you!