Of course, such changes could also be caused by being stressed in general. Even if you could calibrate your model to separate the effects of "being under duress" from "being generally stressed" in a particular subject, I would presume that there's too much variability in people that you could do this reliably for everyone.

Imagine how people would react to an ATM that gave them their money whenever they wanted it - except when they were in a big hurry and really needed the cash now.