Mental disorder
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.
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