The article doesn't talk about aggression. I'd be interested in seeing some good quality research comparing people's responses to stuff when they're had caffene vs not.
It's frustrating that the evidence around mental health is so poor. I think that small amounts of caffeine destroy my sleep hygiene so I avoid it after midday. But it'd be great to know if a couple of cups of coffee in the morning was probably good or probably not good.
Just to add another data point - I seem to be very sensitive to caffeine, too. Any more than a small cup of coffee in the morning will lower my sleep quality.
Sometime I find myself getting strangely aggressive about things if I have, say, two small cups of coffee. It helps a lot to get me going in the morning, but I have to be very careful, and take frequent vacations. I used to be able to drink a lot of coffee, too much, but I've gotten much more sensitive as I've gotten older.
Better would be to separate decaf and fully caffeinated grinds into numbered packages, keep a sleep journal, and then after three weeks see if there were any meaningful difference. Otherwise the results are going to be heavily influenced.
It's frustrating that the evidence around mental health is so poor. I think that small amounts of caffeine destroy my sleep hygiene so I avoid it after midday. But it'd be great to know if a couple of cups of coffee in the morning was probably good or probably not good.