Editing Mental disorder (section)

==Classifications==
{{Main|Classification of mental disorders}}

There are currently two widely established systems that classify mental disorders:
* ''ICD-11 Chapter 06: Mental, behavioural or neurodevelopmental disorders'', part of the [[International Classification of Diseases]] produced by the WHO (in effect since 1 January 2022).<ref>{{Cite web |title=ICD-11 for Mortality and Morbidity Statistics |url=https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/334423054 |access-date=2022-08-13 |website=icd.who.int |archive-date=1 August 2018 |archive-url=https://archive.today/20180801205234/https://icd.who.int/browse11/l-m/en%23/http://id.who.int/icd/entity/294762853#/http://id.who.int/icd/entity/334423054 |url-status=live }}</ref>
* ''[[Diagnostic and Statistical Manual of Mental Disorders]]'' (DSM-5) produced by the APA since 1952.

Both of these 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, for example, the ''[[Chinese Classification of Mental Disorders]]'', and other manuals may be used by those of alternative theoretical persuasions, such as the ''[[Psychodynamic Diagnostic Manual]]''. In general, mental disorders are classified separately from [[neurological disorders]], [[learning disabilities]] or [[intellectual disability]].

Unlike the DSM and ICD, some approaches are not based on identifying distinct categories of disorder using [[Dichotomy|dichotomous]] symptom profiles intended to separate the abnormal from the normal. There is significant scientific debate about the relative merits of categorical versus such non-categorical (or hybrid) schemes, also known as [[Continuum (theory)|continuum]] or dimensional models. A [[spectrum approach]] may incorporate elements of both.

In the scientific and academic literature on the definition or classification of mental disorder, one extreme argues that it is entirely a matter of value judgements (including of what is [[norm (sociology)|normal]]) while another proposes that it is or could be entirely [[objectivity (science)|objective]] and [[scientific]] (including by reference to statistical norms).<ref>{{cite journal | vauthors = Berrios GE | title = Classifications in psychiatry: a conceptual history | journal = The Australian and New Zealand Journal of Psychiatry | volume = 33 | issue = 2 | pages = 145–60 | date = April 1999 | pmid = 10336212 | doi = 10.1046/j.1440-1614.1999.00555.x | s2cid = 25866251 | url = https://www.revistas.usp.br/acp/article/view/17193 | access-date = 9 November 2022 | archive-date = 21 February 2024 | archive-url = https://web.archive.org/web/20240221121901/https://www.revistas.usp.br/acp/article/view/17193 | url-status = live }}</ref> Common hybrid views argue that the concept of mental disorder is objective even if only a "fuzzy [[prototype]]" that can never be precisely defined, or conversely that the concept always involves a mixture of scientific facts and subjective value judgments.<ref>Perring, C. (2005) [http://plato.stanford.edu/entries/mental-illness/ Mental Illness] {{Webarchive|url=https://web.archive.org/web/20180611130635/https://plato.stanford.edu/entries/mental-illness/ |date=11 June 2018 }} Stanford Encyclopedia of Philosophy</ref> Although the diagnostic categories are referred to as 'disorders', they are presented as medical diseases, but are not validated in the same way as most medical diagnoses. Some neurologists argue that classification will only be reliable and valid when based on neurobiological features rather than clinical interview, while others suggest that the differing ideological and practical perspectives need to be better integrated.<ref name=Katsching>{{cite journal | vauthors = Katschnig H | title = Are psychiatrists an endangered species? Observations on internal and external challenges to the profession | journal = World Psychiatry | volume = 9 | issue = 1 | pages = 21–8 | date = February 2010 | pmid = 20148149 | pmc = 2816922 | doi = 10.1002/j.2051-5545.2010.tb00257.x }}</ref><ref name=Kato>{{cite journal | vauthors = Kato T | title = A renovation of psychiatry is needed | journal = World Psychiatry | volume = 10 | issue = 3 | pages = 198–9 | date = October 2011 | pmid = 21991278 | pmc = 3188773 | doi = 10.1002/j.2051-5545.2011.tb00056.x }}</ref>

The DSM and ICD approach remains under attack both because of the implied causality model<ref>{{cite web |vauthors=Doward J |date=11 May 2013 |title=Medicine's big new battleground: does mental illness really exist? |url=https://www.theguardian.com/society/2013/may/12/medicine-dsm5-row-does-mental-illness-exist |website=The Guardian |access-date=15 December 2016 |archive-date=28 June 2021 |archive-url=https://web.archive.org/web/20210628184855/https://www.theguardian.com/society/2013/may/12/medicine-dsm5-row-does-mental-illness-exist |url-status=live }}</ref> and because some researchers believe it better to aim at underlying brain differences which can precede symptoms by many years.<ref>{{cite web|url=http://www.nimh.nih.gov/about/updates/2013/mental-disorders-as-brain-disorders-thomas-insel-at-tedxcaltech.shtml |title= Mental Disorders as Brain Disorders: Thomas Insel at TEDxCaltech |website=National Institute of Mental Health |date=23 April 2013 |publisher=U.S. Department of Health and Human Services |archive-url=https://web.archive.org/web/20130507060046/http://www.nimh.nih.gov/about/updates/2013/mental-disorders-as-brain-disorders-thomas-insel-at-tedxcaltech.shtml |archive-date=7 May 2013 }}</ref>

===Dimensional models===
The high degree of [[comorbidity]] between disorders in categorical models such as the DSM and ICD have led some to propose dimensional models. Studying comorbidity between disorders have demonstrated two latent (unobserved) factors or dimensions in the structure of mental disorders that are thought to possibly reflect etiological processes. These two dimensions reflect a distinction between internalizing disorders, such as mood or anxiety symptoms, and externalizing disorders such as behavioral or substance use symptoms.<ref>{{cite journal | vauthors = Hankin BL, Snyder HR, Gulley LD, Schweizer TH, Bijttebier P, Nelis S, Toh G, Vasey MW | title = Understanding comorbidity among internalizing problems: Integrating latent structural models of psychopathology and risk mechanisms | journal = Development and Psychopathology | issn = 0954-5794 | eissn = 1469-2198 | volume = 28 | issue = 4pt1 | pages = 987–1012 | date = November 2016 | pmid = 27739389 | pmc = 5119897 | doi = 10.1017/S0954579416000663 }}</ref> A single general factor of psychopathology, similar to the [[G factor (psychometrics)|g factor]] for intelligence, has been empirically supported. The ''p factor'' model supports the internalizing-externalizing distinction, but also supports the formation of a third dimension of thought disorders such as schizophrenia.<ref>{{cite journal | vauthors = Caspi A, Houts RM, Belsky DW, Goldman-Mellor SJ, Harrington H, Israel S, Meier MH, Ramrakha S, Shalev I, Poulton R, Moffitt TE | title = The p Factor: One General Psychopathology Factor in the Structure of Psychiatric Disorders? | journal = Clinical Psychological Science | volume = 2 | issue = 2 | pages = 119–137 | date = March 2014 | pmid = 25360393 | pmc = 4209412 | doi = 10.1177/2167702613497473 }}</ref> Biological evidence also supports the validity of the internalizing-externalizing structure of mental disorders, with twin and adoption studies supporting heritable factors for externalizing and internalizing disorders.<ref>{{cite journal | vauthors = Forbes MK, Tackett JL, Markon KE, Krueger RF | title = Beyond comorbidity: Toward a dimensional and hierarchical approach to understanding psychopathology across the life span | journal = Development and Psychopathology | issn = 0954-5794 | eissn = 1469-2198 | volume = 28 | issue = 4pt1 | pages = 971–986 | date = November 2016 | pmid = 27739384 | pmc = 5098269 | doi = 10.1017/S0954579416000651 }}</ref><ref>{{cite journal | vauthors = Gizer IR | title = Molecular genetic approaches to understanding the comorbidity of psychiatric disorders | journal = Development and Psychopathology | issn = 0954-5794 | eissn = 1469-2198 | volume = 28 | issue = 4pt1 | pages = 1089–1101 | date = November 2016 | pmid = 27739393 | pmc = 5079621 | doi = 10.1017/S0954579416000717 }}</ref><ref>{{cite journal | vauthors = Lahey BB, Krueger RF, Rathouz PJ, Waldman ID, Zald DH | title = A hierarchical causal taxonomy of psychopathology across the life span | journal = Psychological Bulletin | volume = 143 | issue = 2 | pages = 142–186 | date = February 2017 | pmid = 28004947 | pmc = 5269437 | doi = 10.1037/bul0000069 }}</ref> A leading dimensional model is the [[Hierarchical Taxonomy of Psychopathology]].