The birth of a child or death of a parent examples are to show how much of a life changing event the mystical experience is. It's a measure of impact.
Here's another link;
http://www.hopkinsmedicine.org/Press_releases/2006/07_11_06.htmlThere are a few things that are worth noting about the study.
The people in the study were around 46 years old & they all had a religious background. It was done in an environment meant to reduce the chance of bad trips.
I think that all of these things contributed to the positive outcome of the experiment.