In the history of developing successful diagnostic procedures in medicine, a primary prerequisite has been a fairly precise knowledge of what constitutes normal anatomy and physiological functioning. In other words, before physicians can diagnose illness or disease, they must know the population parameters of ‘‘normal’’ biological functioning. The fact that an understanding of normal behavior is a prerequisite to identify and investigate abnormal …show more content…
Essentially, psychopathology can be defined by two methods: the class model and the multivariate, dimensional, or quantitative model. The multivariate model assumes that all behavior can be placed on a continuum; one example would be intelligence. When some behaviors, such as depression and anxiety, become so exaggerated that their intensity is exhibited by only a small fraction of the population, then psychopathology may be demarcated. In this sense, a disorder such as depression or anxiety is diagnosed in the same way as hypertension in medical classification. When these responses reach a certain frequency, intensity, and duration, they are labeled pathological. Note that to use this criterion, it is necessary to have the population parameters or, in less suitable situations, clinical knowledge of the attribute and to make some judgment about where the limits should be, a judgment that is somewhat arbitrary. Selecting the appropriate limits can be aided by knowledge of the consequences of the extremes of behavior. It is also necessary to know the environmental aspects and other related circumstances of these behaviors (stimulus parameters) to make such a decision. The loss of a loved one, for example, is typically assessed with an increase in depression of high intensity, but of limited duration. Epidemiological inquiry and the notion of prevalence are the key concepts in this approach, although it is important to keep in mind Costello’s warning that merely because behavior patterns are frequent does not mean that they are normal or acceptable. For example, posttraumatic stress disorder is a frequent, albeit arguably ‘‘abnormal,’’ response to traumatic events. The dimensional approach to classification is the essence of this