Research...
There hasn't been enough research on tickling for it to be considered a viable form of medical or therapeutic treatment. Even Reflexoligists shun tickling as a tool for therapy in their experience.
There hasn't been much research on the subject of laughter either. The cause or reason for laughter beyond social expression hasn't really been covered by the masses. It's just something we do. And from what I gather on the net, not many have had the incentive to truly run full exploration on the subject. (One of those, if you can't make money off it things...)
Since tickling has been painted by most psychiatrists as an act that can be construed as either a loving social form of touch and expression, or the other side, an abusive and uncontrolled event that can cause trauma to a victim, the idea of a gradual release of physical and emotional tention through tickling is laughable by medical standards. Since it's too much of a black and white subject in the modern world.
Which is why 'massage therapists' aren't exactly equipped for dealing with schitzophrenic(sp), or emotional depressive patients like these researchers you mention have tried to do. Although tickling in my idea could in theory be something really important if they would only research it further.
I think most of us can agree there is something mysterious to tickling. Truly, what in heaven's plan made a function to our bodies that make us, of all things, laugh involuntarily when touched. A mirthful subject, but when you think about it really, it's quite interesting. Some scientists have said it was a self defense mechanism, such as if a spider were crawling up our back we could feel it and deflect such dangerous occurences, but laughter when applied to certain spots? It's ironic to be laughing as a self-defense mechanism to danger...
More importantly, most of us know that even if one doesn't enjoy the sexual side of tickling like some of us, it can still be a relaxing and active form of releasing anxiety if done in a safe enviroment with people one knows/trusts. The act of bondage itself can be liberating in the right circumstance (Heh, I love how being tied up can set one free eh'? ^.~). But one would have to look at it outside the box. Do we believe this to be so due to our love for tickling, or it as a true scientifical fact? Only research can prove if even the casual passerby would have these results.
Perhaps many people have this same love for all we know but don't explore it due to social taboo. And there is an underlying social taboo with tickling you know...but that's for another thread...
Ahk, I need sleep.
-Ace