The conclusions of the book were a bit depressing: there seems to be no psychological benefit to having a DMT flash.
I think psychological effects are best researched in environments where DMT is used in a traditional way as with Ayahuasca. And I feel that there would be a far better chance of having psychological benefits from a DMT flash, if time/effort was put into preparing for it. Like my most insideful trips with long lasting effects happened after I spend the entire day in anticipation of the experience. Don't share time with other who won't be there during the trip, no shopping, nice long forest walk etc...
Compare this to driving to a hospital, have stuff attached and plugged into your body. Some nurse is nearby for safety, you've mixed with several people and then they trigger an awe inspiring experience in you which blast you of your socks and it lasts only 5 minutes. I don't know, it's just a gut feeling that I have that if you would use it more ritually (as in preparing, clear your head, clean your body, think about where you are, where you want to go etc...) and then have a DMT flash, it could have a longer lasting positive imprint.
What I found interesting is the apparent connection between near death experiences and alien abductions and DMT trips.