Lisa Hamilton, a jeweler and doula in Brooklyn, NY, knows about the side effects. She recently tried CBD for the shoulder pain that plagued her five years after an accident. Her doctor certified that she was in chronic pain, which under New York State law allowed her to buy from a state dispensary. One Friday, she swallowed two 10-mg capsules, the amount recommended at the dispensary, then took another two on Saturday. “By Sunday, it felt like I’d gotten hit by a truck. Every muscle and joint ached,” Hamilton says. She cut back to one pill a day the following week, but still felt hungover. She stopped after that.