Weed makes you depressed because weed causes a dopamine rush and your brain will use it as its primary source of dopamine and stop making it on its own so you become depressed whenever you aren't smoking weed and weed will have a weaker affect every time you smoke it making you more and more depressed. Weed can also make you retarded cuz it kills brain cells. You can literally smoke your yourself retarded. It has happened before. [spoiler]dopamine is the chemical in your brain that makes you feel happy.[/spoiler]