Plants

Altered states typically refer to use of psychoactive or hallucinogenic drugs.

Transitor

The typically alter a persons state of mind, if not they alter somebody physically or biologically. There are negative side affects to all drugs, whether it is to the person doing them or the people around them. The main reason is that it has a negative effect on society.

These are typically known as neuromodulators; they can either change the rate at which a neurotransmitter is released, or alter the response to a certain neurotransmitters.