The role of the “International Classification of Functioning, Disability and Health, ICF” in the description and classification of mental disorders

Diagnoses according to ICD-10 or DSM are conclusions derived from diagnostic algorithms, based on symptoms, but also illness course, history and consequences of the illness state. But, there is only limited consensus about the definitions of the criteria which are the basis of diagnostic algorithms. In DSM there is only a small glossary of technical terms, while ICD does not provide any respective definitions at all. When the diagnostic criteria are unreliable or unvalid, then also the diagnostic conclusions must be invalid, even when they are based on strict algorithms. Therefore, standardized definitions for diagnostic criteria are as important as standardized diagnostic algorithms. The ICF, published by WHO in 2001, defines in it's first chapter mental functions which are identical with descriptions of psychopathological terms, if there is a malfunctioning. As definitions of diagnostic criteria are missing in ICD or DSM, the ICF definitions for functions, and thus disorders of functions, are at present the only glossary of illness signs and symptoms. Therefore, the ICF can serve as the basis for diagnostic algorithms in ICD or DSM. Furthermore, illness definitions are, apart from symptoms, also based on illness consequences. These are also defined in ICF as capacities (or disorders of capacity) and participation. Disorders of functions, capacity and participation together can describe targets of treatment. In summary, ICD and ICF as members of the family of WHO classification systems can together provide a common language for the description of health, illness and treatment goals.