So part 1 showed that caffeine at high enough doses works a little like marijuana and is a pro-psychotic: Insight: Caffeine is a pro-psychotic!.
Part 2 Caffeine is Good Guys was roughly based off this article from Anxiety.Org: Anxious? Drink coffee and focus on something
Part 3: Schizophrenia, Bipolar, ADHD and Depression are cases of what they call hypofrontality or reduced brain blood flow in the thinking and self-regulation part of the brain. https://en.wikipedia.org/wiki/Hypofrontality
It turns out that caffeine reduces blood flow and reduces the diameter of blood vessels in the brain! The Effect of Daily Caffeine Use on Cerebral Blood Flow: How Much Caffeine Can We Tolerate?, Comparison of caffeine-induced changes in cerebral blood flow and middle cerebral artery blood velocity shows that caffeine reduces middle cerebral artery diameter.. So far 1 positive thing about caffeine is that it helps focus (although I’m not sure how this works) and 2 negative things are that it is a pro-psychotic and that it reduces brain blood flow!
Moreover, recent studies have shown that the alpha 2 receptor agonists such as Clonidinie and Guanfacine can treat hypofrontality associated with ADHD, PTSD and depression. (From Wiki).
It is known that Taurine is also an alpha 2 agonist and may reverse hyprofrontality as Cloninide and Gaunfacine do. (Link soon.)