What evidence exists that marijuana is effective in relieving nausea and vomiting?

YES!!! Marijuana has been scientifically proven to cure nausea. That is why it is prescribed by some states for chemotherapy patients; to cure there loss of appetite and their nausea. Don't believe any Propaganda about marijuana. It is one of the most useful "drugs"(I don't even like calling it that) in medicine and cures a variety of different symptoms. It can also be used for Post Traumatic Depression, Anxiety, Glaucoma, Asthma, and numerous others. Check up on your state laws and see if you can get a Medical Marijuana Card if you feel its necessary.