When the Winchesters went into a psychiatric hospital on Supernatural, they weren't just facing a Wraith, they were facing their own psyches. They may have gone a little cuckoo, but "Sam, Interrupted" was one of the more psychological episodes of Supernatural, exploring the root causes behind Sam and Dean's actions.
For Sam, the episode revealed that his rage and violent outbursts aren't connected to drinking demon blood, they're much deeper. This makes sense because, if you're looking for the cause of Sam's current psyche, it goes back long before he met Ruby.
Sam's issues can be traced back to childhood, and they are in the inevitable result of Dean's Hero Complex. He was always the little brother, the one who needed to be protected and sheltered. Dean was raised by John, for better or for worse, but Sam never really got the chance to know either of his parents. Instead, he was raised by Dean, and Dean's willingness to sacrifice everything for Sam prevented Sam from being able to face reality on his own.
He tried to go out into the world and find his own place, but as soon as he fell in love with Jessica, she was killed by Azazel. Sam's one attempt at finding his own way in life ended in tragedy, and since he was shielded as much as possible as a child, he couldn't fully handle the trauma.
Instead, Sam lashed out. Like a jack in the box, he exploded and channeled all of his rage outwardly onto demons. Dean is aware enough of how crappy their lot in life is to turn to booze and women to dull the pain, but repressed Sammy takes out his frustrations on others.
Basically, whether its Dean's boozing and womanizing or Sam's uncontrollably rage, the root cause is abandonment from their father. As awesome as John Winchester was, he wasn't the most emotionally available father.
He forced Dean to grow up too quickly, and as a result, he inadvertently allowed Sam never to grow up at all. The result is two brothers with wildly different approaches to handling their daddy issues. For Sam, that happens to be killing as many demons as possible as violently as possible.
I hate to break it to him, but no matter how many monsters he ganks, his daddy will never come back to comfort him. Unless he builds a field of dreams.
What do you think? Is this analysis dead-on, or am I completely misinterpreting Sam's psyche?