I've never read any of the case data, but among the articles like this I've read it often seems like people's sensitivity and reactions to these neurological drugs varies by a range of 1-8x and the resulting impairment also varies. It also seems like in some people have neurochemistry that self-amplifies effects.

Too bad we don't see long term convert studies on how MDMA has positive treatments affects on soldiers (hard to get funding for that obviously - these studies are all about finding new and better ways to harm the enemy, not help our soldiers)