Caffeine increases dopamine, norepinephrine, and focus/energy by engaging brain circuits and acting through the cyclic AMP-phosphodiesterase pathway.

“Basically coffee gives you energy it makes you feel good and it increases focus because of the circuits that it engages in the brain.”

“caffeine is increasing dopamine's function by changing the number and efficacy of dopamine receptors, but of course, it also increases our wakefulness, our alertness, and that is largely through the neurochemical systems related to adenosine, which is a molecule that builds up in our brain and body the longer we are awake, it's part of the sleepiness system if you will, it makes us feel fatigued or tired, and caffeine also operates on the epinephrine, the adrenaline system.”

“Because caffeine increases the catecholamines and in particular because caffeine increases dopamine transmission in the prefrontal cortex-- this area of the brain that's associated with focus and rule setting and context and task switching-- caffeine is known to improve focus and alertness, in particular, in people who have symptoms of ADHD or other attention and focus issues.”