I don't know about MDMA in particular but over the last years I have seen two times the effect of trips gone wrong. Interestingly both involved women ripping off their clothes (seriously!) and running around screaming at the top of their lungs for hours. One especially was alone in the middle of the LA National Forest hours away from civilization next to pretty big cliffs. I just happened to hike by and could hear her for miles. I never do drugs so I just want to make sure I have someone close who knows what he/she is doing and can handle the situation if I respond weirdly.