I am perhaps the wrong person to make a first comment, as I'm going to be putting my scientist's hat on. And when I say that, I mean I'm going to be skeptical even of my own opinion on the matter. I do science every day now, and have learned to let the data from a well-constructed experiment do the talking. But lacking said data... all we have is expert opinion. That is what it is, and I'll share my own. It's based on having taught over 2000 through the years.
My personal opinion is that this is the classic chicken-and-egg problem to untangle and comment on. Nowhere have we seen people randomized to "train" and "no train" groups. Instead we deal with selection bias where some people self-select to train and some people don't.
To start with, only about 5 percent of the people you train make it to shodan, if that many. The other 19 out of 20 choose to move on in life. That doesn't mean we didn't have an effect on those people; we can never know as they go on to their lives. But I have experienced the anecdotes.
There's that mom who came to me with baby in arms, thanking me for teaching her ukemi. Allegedly her training in my class caused her not to squash baby when she took a fall in the garage with junior in her arms. Another told me how a horse stopped suddenly and he rolled off the horse and on to feet - as if he meant it. And that happened literally a few miles away from where Christopher Reeves broke his neck in a horse-riding accident, permanently altering (and shortening) his life and quite possibly that of his wife.
Another thing I note is the preponderance of professionals amongst my dan ranks. I have a non-representative sample of doctors, lawyers, nurses, and PhDs in scientific fields. The numbers in fact are staggering. Off the top of my head I can think of 4 doctors, 3 physics PhDs, a biology professor, a nursing professor, and a gaggle of lawyers. And then there are a couple of people like the hedonist Bryan who still lives the good life by teaching skiing in the winter (Colorado) and sky diving in the summer (wherever). But what is this all about? Do people bound for professional careers gravitate to and excel in martial arts? Alternately does the training prepare them for the academic work and those careers? Or is there some kind of interaction where they play off each other? I don't know...
I can also say that I have a number of students who either have traveled abroad (Asia) or served in the armed forces after training in my classes. And all have done well. And come back alive. (Knock on wood...)
Personally when I entered Mr. Jefferson's University, I wanted to create my own "University Degree" experience. I wasn't formally accepted into that program, but the advisor I gravitated to (and now founder of VCU's engineering program) understood and supported my goals. I wanted to master biology, chemistry, math, music, and martial arts, and I saw them as one entity. And to me they still are.
Book coming soon.