I think personal experience here is the answer. Even an excellent academic study, peer reviewed, conducted by experts in the field, published in a prestigious journal, is still at best one single experiment. Pretty sure the common answer to this is question is, try it yourself. Do it consistently 10 minutes a day for at least a week and see if you notice any benefit. That should be more informative than any study and as relevant to you as any experiment can be, you are the test subject. Also probably take as long as any review (a thorough one anyways) of academic literature.

If you see a benefit, consider it "proven," if not consider it a still unanswered question. That being said, I recall having once come across some interesting research in neuroscience dealing with meditation. However, it being neuroscience and not psychology, I don't think the research set out to ascertain any proclaimed "perceived" benefits. Just understanding the impact on the brain, neurologically, of meditation. I will try to link if I can recover the source.

All the countless academic studies showing the benefits of meditation are comparing people who meditate vs. people who don't meditate with all else being equal.

What sort of methodology do you suppose can better attribute causality to a subjective experience? This is as far as the scientific method is willing to go, and the results are unanimous.

here's one backing TM: http://www.tm.org/healthpro/downloads/circulation-aha.pdf

there are more, just google it.

i was skeptical as well, but i've found that TM has helped me be a bit more relaxed and 'aware'.

It's been a while since I've read it, but Sam Harris's Waking Up might be something you'd find useful reading.

He describes the benefits of meditation from a skeptic and neuroscientist's perspective.