I've seen it listed as anti-psychotic before. Although I was thinking more like Abilify. I had Tardive Dyskinisia on Abilify, and I was drinking a lot of diet sodas at the time too.
Aspartame is an artificial sweetener. It is common in sugar-free and low-calorie products. It is in most gum, diet sodas, etc. It is in Equal, NutraSweet, Canderel, and AminoSweet.