system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What are the psychoactive effects of nicotine and what is the chemistry behind them?

I recently read an article saying that nicotine is the "world's most popular placebo", in that it only produces a different effect depending on what the individual desires from tobacco. Is this true? Is it known that nicotine actually has any psychoactive effects? If so, how does it do this? Thanks!
gpt
Nicotine has several effects on the brain; first and foremost is an increase in dopamine that stimulates "reward pathways" in the brain. This basically makes you feel good and happy. 

Another effect of nicotine is a "rush", an acute increase in adrenaline that stimulates your body and mind. 

Lastly nicotine can cause a sedative effect and make you tired or less energetic. This follows the initial rush or stimulation initially found in nicotine.