'Not Otherwise Specified' (NOS) in the Diagnosis of Mental Disorders

How This Term Was Used in the Fourth Edition of the DSM

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In the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), which was written and issued by the American Psychiatric Association (APA), "NOS" is an abbreviation for "not otherwise specified." It serves as a sort of catch-all term to label symptoms that don't neatly fall into a well-defined diagnosis, but that clearly indicates that someone is dealing with an illness that's part of a specific family of diagnoses.

An example of this is "Depressive Disorder NOS." A doctor using the DSM-IV to diagnose a patient may have chosen to label that person's diagnosis in this way because although it was clear her symptoms showed she was dealing with a particular type of depression (rather than, say, a panic disorder or an anxiety disorder), there wasn't enough information to home in a specific type of depression, such as dysthymia or bipolar disorder.

Some other examples of "not otherwise specified" mental disorders include:

  • Anxiety Disorder NOS
  • Bipolar Disorder NOS
  • Dissociative Disorder NOS
  • Eating Disorder NOS
  • Gender Identity Disorder NOS  
  • Impulse-Control Disorder NOS
  • Mood Disorder NOS
  • Parasomnia NOS 
  • Personality Disorder NOS
  • Pervasive Developmental Disorder NOS
  • Psychotic Disorder NOS
  • Sexual Dysfunction NOS
  • Somatoform Disorder NOS

Why "NOS" Is No Longer in the DSM

Today you won't find a "NOS" diagnosis for depressive disorder or any other mental disorder in the diagnostic manual. This isn't because there are fewer people with the symptoms but because it is an outdated diagnostic category.

Published by the American Psychiatric Association (APA), the DSM is what clinicians and psychiatrists use to assess and diagnose psychiatric disorders. It is also used for billing as many health insurance providers require a specific diagnosis for approval of payment for treatment.

There have been several versions of the DSM manual since it was first published in 1952 (DSM-1), including the most recent DSM-5 (note that the use of Roman numerals was dropped from the title of the manual), which was published in May of 2013 and contains some significant changes.

This includes the elimination of the catch-all "not otherwise specified" (and NOS) subcategory. The authors have replaced it with "other specified" and "unspecified" to indicate clusters of symptoms that do not neatly fit into another existing category.

Why two terms to replace one? The difference is based on whether a diagnosing doctor chooses to indicate why the diagnostic criteria were not met.

An example of "other specified" might be a depressive episode that does not have the full number of symptoms to meet the formal diagnosis. By contrast, "unspecified" might be used in a situation in which there isn't enough information to make a more specific diagnosis.

According to the APA, "unspecified" allows doctors to provide patients with the best possible care in, for example, emergency situations when there isn't time to get all the information necessary to make a solid diagnosis, but treatment is nevertheless needed.

An "unspecified" label will allow a physician to be as specific as possible in his diagnosis without necessarily showing that a patient meets the full criteria for a given diagnosis.

For example, in an emergency room setting, the medical professional on staff can use the diagnosis of "unspecified depressive disorder" for problems that do not meet the full criteria for any of the disorders in the depressive disorders diagnostic class or if there simply isn't enough information for a conclusive diagnosis.

Making Diagnoses More Universal

Replacing "NOS" brings the DSM-5 more in line with the World Health Organization's International Classification of Diseases (ICD). This diagnostic tool is "the foundation for the identification of health trends and statistics globally and the international standard for reporting diseases and health conditions. It is the diagnostic classification standard for all clinical and research purposes," according to the World Health Organization's website. The ICD requires mandatory codes for disorders that do not precisely fit current definitions for major disorders.

So how will this change impact you? While reclassifying mental disorders and making them more universal won't change the symptoms associated with your specific condition, it will hopefully enable mental health professionals to formulate a more tailored treatment plan that addresses your individual symptoms, needs, and overall health.

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