Several criteria exist for defining a psychological disorder. Sometimes a person needs to meet only one criterion to be diagnosed as having a psychological disorder. In other cases, more than one of the following criteria may be met:
Example: Ted’s delusion that he is a prophet causes him to stand at street corners lecturing people about the morality of their behavior.
Example: Bethanne’s excessive use of alcohol makes her unable to hold down a job.
Example: David suffers from chronic and painful anxiety.
Psychologists use different conceptual models for understanding, describing, and treating psychological disorders.
The medical model is a way of describing and explaining psychological disorders as if they are diseases. Many terms used to discuss psychological disorders come from the medical model. Diagnosis refers to the process of distinguishing among disorders. Etiology refers to the cause or origin of a disorder. Prognosis refers to a prediction about the probable course and outcome of a disorder.