Classifications

Main article: Classification of mental disorders

The definition and classification of mental disorders is a key issue for mental health and for users and providers of mental health services. Most international clinical documents use the term "mental disorder". There are currently two widely established systems that classify mental disorders—ICD-10 Chapter V: Mental and behavioural disorders, part of the International Classification of Diseases produced by the World Health Organization (WHO), and the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) produced by the American Psychiatric Association (APA). Both list categories of disorder and provide standardized criteria for diagnosis. They have deliberately converged their codes in recent revisions so that the manuals are often broadly comparable, although significant differences remain. Other classification schemes may be used in non-western cultures (see, for example, the Chinese Classification of Mental Disorders), and other manuals may be used by those of alternative theoretical persuasions, for example the Psychodynamic Diagnostic Manual. In general, mental disorders are classified separately to neurological disorders, learning disabilities or mental retardation.
Unlike most of the above systems, some approaches to classification do not employ distinct categories of disorder or dichotomous cut-offs intended to separate the abnormal from the normal. There is significant scientific debate about the different kinds of categorization and the relative merits of categorical versus non-categorical (or hybrid) schemes, with the latter including spectrum, continuum or dimensional systems.