Sigmund Freud is considered the father of modern psychoanalysis. He divided the psyche into the ego, superego and id. The ego is the organized mediator between the person inside and what is going on in the person's environment. The superego is sort of like the conscience and has internalized experiences related to rules, guilt, morality and other issues of right and wrong. The id is driven by our instinctive needs. Freud also looked at the development of the person in psycho sexual stages. A person who did not complete all these stages could become fixated. A person fixated at the oral stage might be overly dependent on others and also show the mouth such as smoking and eating.

             Freud also noted behaviors the ego uses to protect itself. In compartmentalism, the person separates sets of behaviors. He might be very honest with his customers but cheat on his income tax and separate the two events so he can mostly think of himself as honest. In compensation, the person ignores weaknesses and exaggerates strengths. Denial blocks the reality of painful or threatening events. In displacement, the person takes his thoughts and feelings and replaces them with something less threatening. He can't tell the boss off so he kicks the dog. Others include fantasy, intellectualization, projection, where the person sees his flaws in others instead of himself, reaction formation, regression, repression, and sublimation.

             In the cognitive approach, the psychologist considers thinking, or cognition, and how it affects personality and behavior. The medical model recognizes that some psychological problems can have a physical cause, or physical conditions that contribute to them. .

             Most treatment plans are somewhat eclectic. That is, the psychologist picks and chooses the best from each model to provide the best possible support for his or her client or patient.