Response to Commentaries on "The Ketamine Model of the Near-Death Experience ..."

The commentators on my paper raised several interesting issues. Set and setting do influence drug effects, but they also influence near-death experiences (NDEs). Some NDEs are very anxiety-generating, just like some ketamine experiences, though frightening NDEs have been ignored by most researchers. High frequency, compulsive ketamine use is rare. While dimethyltryptamine (DMT) may induce NDEs, this is far from typical, while NDE-like effects are typical of ketamine. Rapidity of onset is not related to the capacity of a drug to induce NDEs. The reality of endopsychosins is doubtful, but the reality of N-methyl-D-aspartate (NMDA) blocking mechanisms is not. NDEs and dream sleep may involve similar mechanisms. Altered states of consciousness do not require a normally functioning brain. Finally, I discuss the possible evolutionary advantage of the NDE mechanism.