DeviCatx
I can agree with this from personal experience. I read somewhere that eating refined grains wrecks havoc on the productions of chemicals and bacteria and the intestine which can in turn inhibit the production of chemicals like serotonin see this link here, and this link as well.
I had already cut out fast food for the most part a couple of months ago and drank diet cola instead. Two weeks ago I took the next step and cut out all refined grains period. The biggest change I've noticed so far is that I don't need to take power naps during the day anymore like I use to, and since I'm eating way more veggies, fruits, nuts, dairy and meat now, it takes way less food than it use to to fill me up. My calorie intake has gone from being 2500 to 1400 per day now.
It's also been said that when you eat refined grains that it's as bad as a chocolate bar. You get a rush, it hits the blood stream way too quick and because there's an excessive amount of energy it gets stored in your body as fat, making your blood sugar levels drop and feeling lethargic. Eating proteins and high fiber keeps the energy super consistent in your blood.
Those links didn't work for me. But yeah. That makes sense. but sounds mostly like you're just talking about it from a health standpoint. I am already aware that you those foods make me lack energy. But it does make sense that can be a contributing factor to lead to depression. like some have already said.