Are there really only 2 kinds of people in the world? Evaluating the distribution of change from baseline in pain clinical trials

It is often assumed that there are 2 types of pain patients: those who respond well to efficacious pain therapies and those who do not respond at all, with few people in the middle. This assumption is based on research that claims that changes in pain intensity have a bimodal distribution. The claim of bimodality has led to calls for a change in how pain clinical trials are designed and analyzed, eg, performing “responder” analyses instead of...