The website and wikipedia article about transcendental meditation raises some huge red flags, looks a lot like a sect.
After further research, there is no scientific proof nor studies that would demonstrate the effectiveness of this method.
I would not underestimate the placebo effect, but a method where the name is a trademark, and can only be taught by people part of the organization seems too fishy.
If it is so effective, why is it not part of psychology curriculums?