Mental illness is one of those issues that not even smart people have a good grasp of. So we probably shouldn't be surprised that Hollywood's treatment of it is about as informed and respectful as showing up drunk to a stranger's funeral and crapping in the casket.
From serial killer movies to sappy mental hospital dramas, Hollywood uses mental illness as a convenient plot point, often forgetting to do even five minutes of Googling on the subject first. As a result we get things like...
6The Magic Key/Instant Cure
On the Season 6 premiere of House, our hero discovers that a catatonic patient is constantly staring at something in the nurses' office. Anyone without House's keen intellect would've assumed that "something" was a ham sandwich, but House discovers that it's actually a music box which, when played, brings this particular patient back to the land of not pissing on herself in the corner (keep in mind this is something the staff has failed to notice for years, but Hugh Laurie spots in a single goddamn day).
But it's not just in medical dramas. We've seen this in pretty much all of the Hannibal Lecter movies (figuring out the one thing that makes the killer an insane murder machine allows the cops to predict who, when and where he'll strike next) and in every film where the primary villain gets talked out of his psychotic master plan by a hero that "understands" him.
Hell, that's even the ending of Spider-Man 2: Spidey talking Doc Ock out of his murderous insanity. "You're completely right, Spider-Man, I did say that people need to let dreams go sometimes. To Hell with my dead wife and everything else that I've lost, I'm totally pulling this fusion reactor on top of myself to save the lives of all the people I was hell-bent on vaporizing mere seconds ago."
In the medical community, this phenomena is known as "complete and utter whale shit" , but in Hollywood it's call it "the magic key."
"Just stick this in your crazy hole and we'll unlock the sanity!"
See, Hollywood is convinced that sometimes there is just one specific thing that has to be discovered in order to cure a person of their shoelace-eating lunacy--or at least unravel the mystery behind it--long-term treatment and medication be damned.
Why It's Bullshit:
Simply put, psychology is not a game of Jenga, wherein one crucial block can bring down the entire tower of mental illness. No one factor made the person snap, and shoving one thing back into place won't make them whole. If it did, this mental illness stuff would be easy.
In the real world people with severe personality disorders are about as predictable as the weather, and so far the fact that we all know what causes lightning hasn't helped us figure out when and where it's going to strike with any kind of certainty.
For instance, think about all those cinematic serial killers brought to justice by the cunning insight of a psychological profiler. In real life that shit only leads to arrests about two percent of the time. The linked Malcolm Gladwell article took a comprehensive look at serial killer profiling and found that it's nothing more than cold reading - a parlor trick utilized by old-timey magicians and psychics to con people into thinking their mind was being read. People want to believe that Sherlock Holmes and his modern day incarnation, Dr. House (or Ben Matlock for you high-brow types) really exists. In reality, the only cases of successful psychological profiling were heavily doctored by the profilers themselves to make their predictions seem more accurate.
"And here's where I'll tell them the killer's address instead of screwing up everyone's lunch order like I actually did!"