Marijuana is the slang term for portions of the Cannabis plant. It is one of the oldest psychoactive substances used by man. Marijuana, also called pot, weed, ganja, mary jane, and a host of other nicknames, is made from the Cannabis plant, which has three species: Cannabis sativa, Cannabis indica and Cannabis ruderalis.
#1. Feel good chemical
This binding in turn triggers a chemical cascade that eventually stimulates the production of dopamine, a brain chemical often called the “feel good chemical,” which is part of the body’s reward system,” said Mitch Earleywine, a psychology professor at the University at Albany in New York, who studies marijuana’s health effects. Source