Different perspectives of validity in psychiatry.

It is important to improve our understanding about what might be the specific characteristics of mental disorders to strengthen the scientific credibility of psychiatry and to clarify its position among other medical and nonmedical sciences. On the other hand, this issue has diagnostic, research, therapeutic, legal, financial, and moral implications. Some authors defend a realistic and absolutist attitude towards validity and others an instrumental and relativistic stance. Regarding the organization of concepts, dimensional or categorical approaches have both advantages and disadvantages. Regarding the methodology by which validity is sought, it can be oriented externally or internally to the concept in question. On the other hand, the validity can be expert driven or data driven, the research can be based on disorders or in symptoms and quantitative or qualitative methods may be used. In this article, we review all these different kinds of perspectives that can be taken towards the definition of validity in psychiatry and the methodology to search for it.