It's true that you can't "hypnotize someone". They do it to themselves! You just talk them through it. That's why nobody can be forced to be hypnotized...although if you're sneaky you can do it discretely enough they don't notice themselves slipping into trance (covert hypnosis). Actually, covert hypnosis is often easier than overt hypnosis, because if someone realizes that you are trying to hypnotize him, he is apt to interfere with the process even if he WANTS to be hypnotized.
The "placebo effect" is actually VERY interesting. You see, your brain has a lot of control over bodily functions. Sometimes slipping someone a placebo is enough to "communicate" to the unconscious parts of the brain that they need to do something to cause the desired effect. In other words, sometimes placebos actually cause the desired effect, simply because people have more indirect control over the unconscious parts of their brains than they realize (they just don't necessarily know how to consciously make it happen--which is where the placebo comes in), and the unconscious part of the brain has a lot of control over body functions. Remember the biofeedback experiments of the 1970s? Same thing, only without machines.
In that case--versus just placating a hypochondriac by giving them "medicine"--the placebo has a real effect.
Hypnosis can often do something similar, but without any deception and a lot more directly. You could, for example, raise or lower your own body temperature if you know how! Fakirs used to have a lot of tricks like that. One named Tara Bey used to do a trick involving blocking pain reception when his cheeks were stabbed--and he used to ask, before the demonstration, "bleeding, or no bleeding?". He could control the bleeding too.
Harry Houdini contributed to his untimely demise trying to prove that these self-hypnotic tricks were fakes. He tried the "water burial" trick, and died a few weeks later, probably weakened by the stunt. Hamid Bey then broke Houdini's record by a factor of two (he stayed underwater for 3 hours, twice as long as the 1.5 hours that did in Houdini).
What he was doing, of course, was going into a deep, cataleptic trance, and drastically reducing his metabolism, breathing, and probably even his body temperature.
In the case of hypnotherapy for emotional problems--well, guess what, emotions are regulated by the brain too, and they too can be manipulated. If someone has some sort of dysfunctional emotional reaction--say, because of a traumatic experience or life-episode, such as an incestuous relationship--yes, that can be fixed. Probably a lot faster than 5-7 years.
It works for most but not all addictive behaviors too. Smoking is really easy--that's why hypnosis clinics are popular for stop-smoking programs. Weight loss, too, if it doesn't involve a complicated medical issue. Alcohol is for some reason harder to treat, although a few specialists do. This is actually related to other subconscious regulation of body functions--hypnosis can treat some of the withdrawal symptoms--possibly even negate them.
