Distressing thought or behavioral pattern
Medical condition
A mental disorder, also referred to as a mental illness, a mental health condition, or a psychiatric disability, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. A mental disorder is also characterized by a clinically significant disturbance in an individual's cognition, emotional regulation, or behavior, often in a social context. Such disturbances may occur as single episodes, may be persistent, or may be relapsing–remitting. There are many different types of mental disorders, with signs and symptoms that vary widely between specific disorders. A mental disorder is one aspect of mental health.
The causes of mental disorders are often unclear. Theories incorporate findings from a range of fields. Disorders may be associated with particular regions or functions of the brain. Disorders are usually diagnosed or assessed by a mental health professional, such as a clinical psychologist, psychiatrist, psychiatric nurse, or clinical social worker, using various methods such as psychometric tests, but often relying on observation and questioning. Cultural and religious beliefs, as well as social norms, should be taken into account when making a diagnosis.
Services for mental disorders are usually based in psychiatric hospitals, outpatient clinics, or in the community, Treatments are provided by mental health professionals. Common treatment options are psychotherapy or psychiatric medication, while lifestyle changes, social interventions, peer support, and self-help are also options. In a minority of cases, there may be involuntary detention or treatment. Prevention programs have been shown to reduce depression.
In 2019, common mental disorders around the globe include: depression, which affects about 264 million people; dementia, which affects about 50 million; bipolar disorder, which affects about 45 million; and schizophrenia and other psychoses, which affect about 20 million people. Neurodevelopmental disorders include attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and intellectual disability, of which onset occurs early in the developmental period. Stigma and discrimination can add to the suffering and disability associated with mental disorders, leading to various social movements attempting to increase understanding and challenge social exclusion.
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Definition.
The definition and classification of mental disorders are key issues for researchers as well as service providers and those who may be diagnosed. For a mental state to be classified as a disorder, it generally needs to cause dysfunction. Most international clinical documents use the term mental "disorder", while "illness" is also common. It has been noted that using the term "mental" (i.e., of the mind) is not necessarily meant to imply separateness from the brain or body.
According to the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), published in 1994, a mental disorder is a psychological syndrome or pattern that is associated with distress (e.g., via a painful symptom), disability (impairment in one or more important areas of functioning), increased risk of death, or causes a significant loss of autonomy; however, it excludes normal responses such as the grief from loss of a loved one and also excludes deviant behavior for political, religious, or societal reasons not arising from a dysfunction in the individual.
DSM-IV predicates the definition with caveats, stating that, as in the case with many medical terms, "mental disorder" "lacks a consistent operational definition that covers all situations", noting that different levels of abstraction can be used for medical definitions, including pathology, symptomology, deviance from a normal range, or etiology, and that the same is true for mental disorders, so that sometimes one type of definition is appropriate and sometimes another, depending on the situation.
In 2013, the American Psychiatric Association (APA) redefined mental disorders in the DSM-5 as "a syndrome characterized by clinically significant disturbance in an individual's cognition, emotion regulation, or behavior that reflects a dysfunction in the psychological, biological, or developmental processes underlying mental functioning." The final draft of ICD-11 contains a very similar definition.
The terms "mental breakdown" or "nervous breakdown" may be used by the general population to mean a mental disorder. The terms "nervous breakdown" and "mental breakdown" have not been formally defined through a medical diagnostic system such as the DSM-5 or ICD-10 and are nearly absent from scientific literature regarding mental illness. Although "nervous breakdown" is not rigorously defined, surveys of laypersons suggest that the term refers to a specific acute time-limited reactive disorder involving symptoms such as anxiety or depression, usually precipitated by external stressors. Many health experts today refer to a nervous breakdown as a "mental health crisis".
Nervous illness.
In addition to the concept of mental disorder, some people have argued for a return to the old-fashioned concept of nervous illness. In "How Everyone Became Depressed: The Rise and Fall of the Nervous Breakdown" (2013), Edward Shorter, a professor of psychiatry and the history of medicine, says:
 ;templatestyles src="Template:Blockquote/styles.css" / ;About half of them are depressed. Or at least that is the diagnosis that they got when they were put on antidepressants. ... They go to work but they are unhappy and uncomfortable; they are somewhat anxious; they are tired; they have various physical pains—and they tend to obsess about the whole business. There is a term for what they have, and it is a good old-fashioned term that has gone out of use. They have nerves or a nervous illness. It is an illness not just of mind or brain, but a disorder of the entire body. ... We have a package here of five symptoms—mild depression, some anxiety, fatigue, somatic pains, and obsessive thinking. ... We have had nervous illness for centuries. When you are too nervous to function ... it is a nervous breakdown. But that term has vanished from medicine, although not from the way we speak... The nervous patients of yesteryear are the depressives of today. That is the bad news... There is a deeper illness that drives depression and the symptoms of mood. We can call this deeper illness something else, or invent a neologism, but we need to get the discussion off depression and onto this deeper disorder in the brain and body. That is the point.
 ;templatestyles src="Template:Blockquote/styles.css" / ;In eliminating the nervous breakdown, psychiatry has come close to having its own nervous breakdown.
 ;templatestyles src="Template:Blockquote/styles.css" / ;Nerves stand at the core of common mental illness, no matter how much we try to forget them.
 ;templatestyles src="Template:Blockquote/styles.css" / ;"Nervous breakdown" is a pseudo-medical term to describe a wealth of stress-related feelings and they are often made worse by the belief that there is a real phenomenon called "nervous breakdown".
Classifications.
There are currently two widely established systems that classify mental disorders:
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 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 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 normal) while another proposes that it is or could be entirely objective and scientific (including by reference to statistical norms). 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. 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.
The DSM and ICD approach remains under attack both because of the implied causality model and because some researchers believe it better to aim at underlying brain differences which can precede symptoms by many years.
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. A single general factor of psychopathology, similar to the 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. 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. A leading dimensional model is the Hierarchical Taxonomy of Psychopathology.
Disorders.
There are many different categories of mental disorder, and many different facets of human behavior and personality that can become disordered.
Anxiety disorders.
An anxiety disorder is anxiety or fear that interferes with normal functioning may be classified as an anxiety disorder. Commonly recognized categories include specific phobias, generalized anxiety disorder, social anxiety disorder, panic disorder, agoraphobia, obsessive–compulsive disorder and post-traumatic stress disorder.
Mood disorders.
Other affective (emotion/mood) processes can also become disordered. Mood disorder involving unusually intense and sustained sadness, melancholia, or despair is known as major depression (also known as unipolar or clinical depression). Milder, but still prolonged depression, can be diagnosed as dysthymia. Bipolar disorder (also known as manic depression) involves abnormally "high" or pressured mood states, known as mania or hypomania, alternating with normal or depressed moods. The extent to which unipolar and bipolar mood phenomena represent distinct categories of disorder, or mix and merge along a dimension or spectrum of mood, is subject to some scientific debate.
Psychotic disorders.
Patterns of belief, language use and perception of reality can become dysregulated (e.g., delusions, thought disorder, hallucinations). Psychotic disorders in this domain include schizophrenia, and delusional disorder. Schizoaffective disorder is a category used for individuals showing aspects of both schizophrenia and affective disorders. Schizotypy is a category used for individuals showing some of the characteristics associated with schizophrenia, but without meeting cutoff criteria.
Personality disorders.
Personality—the fundamental characteristics of a person that influence thoughts and behaviors across situations and time—may be considered disordered if judged to be abnormally rigid and maladaptive. Although treated separately by some, the commonly used categorical schemes include them as mental disorders, albeit on a separate axis II in the case of the DSM-IV. A number of different personality disorders are listed, including those sometimes classed as "eccentric", such as paranoid, schizoid and schizotypal personality disorders; types that have described as dramatic or emotional, such as antisocial, borderline, histrionic or narcissistic personality disorders; and those sometimes classed as fear-related, such as anxious-avoidant, dependent, or obsessive–compulsive personality disorders. Personality disorders, in general, are defined as emerging in childhood, or at least by adolescence or early adulthood. The ICD also has a category for enduring personality change after a catastrophic experience or psychiatric illness. If an inability to sufficiently adjust to life circumstances begins within three months of a particular event or situation, and ends within six months after the stressor stops or is eliminated, it may instead be classed as an adjustment disorder. There is an emerging consensus that personality disorders, similar to personality traits in general, incorporate a mixture of acute dysfunctional behaviors that may resolve in short periods, and maladaptive temperamental traits that are more enduring. Furthermore, there are also non-categorical schemes that rate all individuals via a profile of different dimensions of personality without a symptom-based cutoff from normal personality variation, for example through schemes based on dimensional models.
Neurodevelopmental disorders.
Neurodevelopmental disorders is a group of mental disorder that affect the central nervous system, such as the brain and spinal cord. These disorders can appear