Statistically speaking, nitrox does and does not do a lot of things. But on an individual basis, statistics are meaningless.
For instance, the chance of getting killed by an asteroid is vanishingly small. But if you are the person who is killed by an asteroid, that statistic is meaningless.
Now I am extremely cynical and belive that the placebo effect accounts for 90% of everything. But if we consult the dictionary:
Sometimes known as non-specific effects or subject-expectancy effects, a so-called placebo effect occurs when a patient's symptoms are altered in some way (i.e., alleviated or exacerbated) by an otherwise inert treatment, due to the individual expecting or believing that it will work.
If you are not expecting a response then it cannot be considered a placebo response.
I dove nitrox daily for 2 weeks in order to get enough nitrox dives under my belt to take an advanced nitrox course. I wasn't expecting any advantages, I was just doing it to get the dives in my log book.
I noticed that I was able to dive 4 times a day without the exhaustion that I noticed on other dive trips that limited me to 2 or 3 dives per day. Screw the statistics, I'm hooked on nitrox.