Which of the following is a an addictive drug that mimics the properties of an natural brain substance?

Question

1.psychedelics

2.stimulants

3.opiates

4.depressants

Answer 1

Opiates  

Answer 2

opiates is the obvious answer, they mimic the function of endorphins...like if this is a test question, that is the answer.

though I would answer this question as "all of the above" - anything that alters perception is mimicking the properties of a natural brain substance.