When it comes to acting, I’ve read and watched interviews with actors explaining how they inhabit the characters they play. In some cases, a few of them have had a hard time separating themselves from the characters, even going so far as to seek professional help in order to get back into their own psyche.
This got me thinking about writers and the characters we create in our fiction. It’s said that all writers put a little bit of themselves into their stories. I agree with that. I know that once I’ve finished a story I can look back over it and see little pieces of myself in there, like my experiences and my personality.
But with that, can writers experience the same situation as some of those actors, where we end up having trouble separating ourselves from the characters we create? 
I don’t see it happening with short fiction, although I assume it’s possible. With short fiction, we aren’t interacting with the characters for a long stretch of time. It’s sort of like participating in a one-act play. I don’t think there’s enough time to really immerse oneself into the character for it to become a problem.
With longer fiction, however, I could see that happening. And not just novels, but also longer plays and movie scripts. In these cases, the writer is spending long periods of time with the characters, especially the protagonist. For long-form work, we have to get inside the character’s head, figure out what motivates them, what they want, their background, their personalities, their hopes and fears. In a way, it isn’t too far removed from acting.
What I’m curious about is if any authors have been so wrapped up in a story they were writing that they had a hard time separating themselves from the characters. Think about some of the more intense characters you’ve encountered in fiction, movies, plays. Consider Patrick Bateman in American Psycho, or Humbert Humbert in Lolita, or Captain Ahab in Moby Dick. All very intense, conniving personalities. How could an author not get tangled up in their creations?
For actors, in most cases, they are inhabiting a character that was created by someone else. They look at a script as a blueprint, and from there they piece it together. In the situations where the script was based on a novel, they may even read the book to get more depth. But for a writer, the characters begin and end in their heads. There isn’t any separation, no division between the two. 
Oddly, I don’t think I’ve ever read of an author having the same issues as an actor when it comes to keeping a distance between themselves and the characters. I wonder why that is? Perhaps writers have more control. I mean, we are the ones creating the characters out of thin air. It’s easy enough to kill them off if we want to, or put them through traumatic experiences to teach them a lesson. Hell, we can simply highlight their existence and hit the ‘delete’ key. A snap of the fingers and they never existed.
I’d be interested to see some research into this, especially if it explains how writers can seemingly get away with having characters live in their heads. And no, I don’t think it’s because we’re all a little crazy.
At least, I hope not.
RB