> Caffeine is a stimulant, which means it increases activity in your brain and nervous system. It also increases the circulation of chemicals such as cortisol and adrenaline in the body.
Extremely unlikely. Caffeine is one of the most studied substances on earth. It's not a secret that it causes a clear physiological response. There are tons of double blind placebo studies on this.
It's not even that. It's just blocking the receptors that tell your brain that it's tired.
You are still exactly as tired as you were, you just don't feel it.
It's marginally less dumb than nicotine when ingested routinely.