Enhancing research and treatment of mental disorders with dimensional concepts: Toward DSM-V and ICD-11

The current versions of the DSM (DSM-IV-TR) and ICD (ICD-10) describe all mental disorders as polythetic-categorical concepts. Lists of symptoms are presented, and diagnostic category labels are assigned to patients based on observing specific patterns of symptoms. A number of notable conceptual problems emerge when using this strictly categorical system in research and in the clinic. When thorough structured diagnostic interviews are used, typical patients meet criteria for more than one specific diagnosis (a phenomenon termed "comorbidity"). In addition, groups of patients with the same putative categorical label are often heterogeneous with respect to key clinical features, such as severity and prognosis, and patients with symptomatology below diagnostic thresholds are often significantly impaired. Although categorical concepts will always be essential in official nosologies (e.g., in providing diagnostic labels for reimbursement purposes), many of the conceptual problems of a strictly categorical diagnostic system can be overcome by enhancing official nosologies with dimensional concepts. Specific dimensional approaches and directions that may be considered for upcoming revisions of both the DSM and ICD are discussed.