One day their father goes missing on what they refer to as a "hunting trip", and Dean seeks out Sam at college to come with him and find their father. They then begin a long journey, fighting the supernatural and helping others along the way with the help of a family friend named Bobby Singer (Jim Beaver), searching for the demon who killed their mother. The character portrayed by Jarred Padlock, Sam Winchester, stands out the most in regards to having a disorder.
He appears to be a paranoid schizophrenic, displaying many symptoms over a period of a few years. After leaving to help his brother find their father, his girlfriend soon dies a similar death to that of his mother, or so he believes, as he begins to experience illustrations that he refers to as 'Visions". Later in the first season, he convinces himself that he must go through 'trials", and at one point believes that he must give up his life to demons that are after him in order to save his brother and a group of strangers.
This could be another delusion of grandeur, as well as a sign of depression (the need to commit suicide) which is an early warning sign of schizophrenia. Later on in season two after finding their father, all three of the Winchester men are in a car wreck that leaves Dean and their father John in critical condition. After his father passes from his fatal wounds and his brother lives, Sam believes that his father sold his soul to a demon in exchange for his brother to live. As the series progresses, Sam becomes more and more socially withdrawn, another early sign of schizophrenia.
His brother becomes his only constant interaction with people. Often in the show he is seen drinking to excess, becoming drunk and sometimes passing out. In many different episodes he stays awake, passing off on sleep to read more on the demons he believes are after him and his rather, occasionally going off on his own to find enemies and kill them. A red flag warning sign of schizophrenia is extreme reaction to criticism, which Sam often experiences, particularly in regard to his father.
In an early episode, Dean and Sam fight about carrying on the family business, as Sam believes it isn't their responsibility and that their father consumed their life with that nonsense rather than allowing them to live normal lives. Dean then tells Sam how he is a coward and selfish, and Sam goes off into a rage, furious at the words of his brother. Whenever he is reprimanded or insulted in the show, he often goes off by himself in a state of anger, sometimes resorting to drinking as a means of getting his mind off of the problem.
Sam also experiences suspiciousness that comes with his hallucinations/delusions. In a later episode he hallucinates that his brother is insulting him and telling him how Sam how he hates him along with blaming him for their father's death, but then after coming back to reality he sees that his brother didn't actually say these things, although he carries the suspicion that he truly feels that way bout him. The most apparent sign of schizophrenia in Sam appears to be his lack of emotion and having a flat expressionless gaze in the later seasons.
He becomes detached to his brother, as nearing the last few seasons they have had problems and gone their separate ways many times. He develops resentment towards Dean, still holding on to his dream of living a normal life, so when they do finally come back together he states that it will only be for that time being until the problem at hand is solved. Although they end up tying with one another, the anger Sam holds inside himself is apparent.