self-induced coma and forced awakening (not in the stickies)

...Ok, I checked and there wasn't anything related to my question(s), so here it is: (non-english speaker here)

Backstory:
...My character had an accident, She didn't sustain any major injuries, and hit her head in a very non-threatening way. She just lost coscienceness. However, she didn't wake up like she was supposed to. She fell into coma without any medical reasons. However, she sometimes makes small movements, makes throat sounds, opens her eyes, etc. (It's true: http://en.wikipedia.org/wiki/Coma ). She almost die from a badly placed "food-tube", from a high fever, and a couple other things, but recovers. There are even some times in which she's about to wake up, but relapses quickly. This goes on for about a year, then she's forcefully awakened (by whom is a plot-secret), and after another year or so she has recovered enough of her mobility and indipendence to return home and face her demons.

Question(s):
...Is it possible for the brain to self-induce itself into coma? And to decide to not wake up? I know that some people who were into a coma and woke up talked about strange, sometimes horrific, sometimes wonderful, dreams. What if my character started one of those dreams and, aided by her injuries, thought that it was a real thing (not "the" real thing, there's a difference) and decided to discarge her not-very-lovely reality, albeit without realizing it?

...And most importantly, would she wake up if some strong stimuli (like adrenaline or some drugs) were injected into her body to cause a reaction? (any consequences of this will be addressed another time) I mean, the coma wasn't induced by injuries or drugs or anything else.

...I'd really like to know if somedoby have answers for these.
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