The medical model applied to abnormal behavior. The medical model proposes that it is useful to think of abnormal behavior as a disease and has become the main way of thinking about mental illness today. This view is in stark contrast to how mental illness used to be perceived. Thus, the medical model has brought much needed improvement in patient care. The diagnosis involves distinguishing one illness from another. " Etiology refers to the apparent causation and developmental history of an illness. " Prognosis is a forecast about the probable course of an illness. Deviance the behavior must be significantly different from what society deems acceptable. Maladaptive behavior the behavior interferes with the person"s ability to function. Personal distress the behavior is troubling to the individual. The american psychological association (apa) uses the diagnostic and statistical manual. It is now in its fifth revision and referred to as the dsm-5.