According to Freud, there is unconscious mental process for most of the individual, which cannot be easily represented. It may manifest in form if dreams, puns, slips of tongue etc. The main concept of Freudian psychoanalysis is that the personality of an individual is determined by the childhood development. Freud also creates the three psychic zones, id, ego and superego, which are the structure of our mind. There are always conflicts among there three zones. And we have to repress many of our desires, the tendencies to pleasure and satisfaction. If we have too much pressure about this, then it may lead to many psychological problems, such as Neurosis and Psychosis.
In the film Psycho, Norman was suffering from Schizophrenia, which makes him detached from reality. He was split into two parts, one was he and another was his mother. He failed to overcome pre-Oedipus stage. As his father died when he was very young, he couldn't recognize the authority of a father. He put all his love to his mother because he had no castration complex to make him abandon his desire for his mother. Therefore, he couldn't allow his mother to fall in love with other man. His id made him felt angry, so he killed both of them. However, later his ego told him that murdering is wrong, especially what he done was committed matricide. He felt guilty and had great pressures. These are the reasons why he would suffer from Schizophrenia. He was probably fixated in the annals stage, too, because he had the problems of switching between passivity and aggression. He was over controlled his mother, and at the same time under controlled. He thought that his mother didn't want him to have lovers, too.
The annal fixation of Norman and his failure to overcomt the Oedipus complex are the main cause of his sickness. Therefore, in some way, it is possible to analyze a character by presenting his/her unconciousness and the childhood development.