More and more states are legalizing marijuana, but how exactly does it effect your body? Well, researchers have discovered that marijuana can help treat chronic pain, improve spasticity symptoms caused by multiple sclerosis, and it can help prevent nausea and vomiting caused by chemotherapy. Researchers also found there is no direct link between marijuana and lung, neck, or head cancers. Negatively though, marijuana makes respiratory symptoms worse and causes chronic bronchitis. It can also impair a person's ability to learn, remember, and to keep focus.