Holy Cow, I just had a light bulb moment. My ADHD BF normally pounds tripple, tripple coffee, sports drinks or in the evening has a couple of drinks. I despise the chemical taste of sports drinks and about three weeks ago asked him if he noticed that whenever he drinks them we ended up in a spat. I didn't realize until right now, he has actually stopped drinking them and has leveled out tremendously in terms of temperament.
Not sure what the scientific side of things is but am sure they have a negative affect.