Ok, turns out you are a collection of something like
1000 different species, most of them in your gut.
You have ten times more bacteria than cells in your body, and it can be fairly said that as far as your body is concerned, you are sharing it with bacteria for just as long as they let you.
These bacteria have a direct line to the brain via the vagus nerve, and can/will alter your brain chemistry, via cytokines, trytophan (precursor for serotonin, bad gut=lower tryptophan=lower serotonin=depressed).
The jury is starting to come back in in this area, and the verdict is increasingly "feed your bacteria properly, or about 999 of you are not going to be happy."
Consider probiotics, any way you can get them, and investigate how you might be killing your bacteria without meaning to, and overcome depression! Deficiencies in Omega 3 and Vitamin D, both essential nutrients that have been stripped from our food supply and that YOU are almost surely deficient in if you are not supplementing, will have similar effects.
from the Feb 2012 "Nutrition Reporter."
https://www.google.com/webhp?rls=ig#...w=1228&bih=615
Can't believe Jack is still giving it away, wow. The "NR" archives provide a wealth of nutrition info, with nothing to buy.