Diagnostic classification past, present, and future: implications for pharmacotherapy

Making a diagnosis is a key step in understanding the natural course of a disorder, selecting an appropriate treatment for the disorder, and predicting its response to treatment. Diagnostic proposals can be evaluated in two ways: reliability and validity. The reliability and validity of diagnoses are not one and the same, although establishing reliability is usually a necessary step before being able to evaluate and determine validity. There is little evidence that most psychiatric diagnoses are valid, but the reliability of diagnoses using classification systems developed since 1970 have greatly improved and are important for clinical practice and research. Past and current diagnostic systems have not optimally assisted the search for disorder-specific pathophysiological mechanisms, and they do not provide the specificity that clinicians would like when selecting medication. The Research Domain Criteria project is intended to shift research away from categorical diagnoses to focus on dysregulated neurobiological systems, and this approach ultimately may be more useful for understanding the pathophysiology of mental disorders and improving the development and use of treatment interventions.