That having been said, I think there's something about meditation traditions that come from and are part of monastic traditions vs. meditation techniques that have been removed from their monastic roots.
Basically, he was meditating at monk-like levels, and if he were actually in a monastery, he would probably have gotten help at some point beforehand. Maybe he was neglecting part of his health, or emphasizing one technique over another without being fully-rounded in his approach, or a number of other similar things that would have been caught by a community/teacher in a monastery. They literally have hundreds of years worth of meditation troubleshooting under their belts, though some of it is codified in ways that directly intertwine with religious beliefs/practices.
But when you try to remove the practice from the culture surrounding it, there's a danger that you left behind some important pieces. I find it kind of scary that he mentions there are recovery groups and such, especially for meditation teachers. I mean, it's awesome that they're supporting each other and recovering, but this seems like a red flag that maybe the a-religious form of meditation as it's being taught and marketed right now needs to go back to the source and figure out what monks are doing differently, or, even better, make sure they immerse themselves deeper into the source cultures to be able to troubleshoot adequately.
I guess it's like eating an olympic athlete's daily meal while ignoring the rest of their training regimen as "religious superstition" and getting drastically different results and being surprised.