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

How This Term Was Used in the DSM-IV

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In the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), published 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 this label if it was clear that the person's symptoms showed they were dealing with a particular type of depression (rather than, say, a panic disorder or an anxiety disorder), but there wasn't enough information to identify a specific type of depression, such as persistent depressive disorder or bipolar disorder.

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

  • 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

You won't find the "NOS" diagnosis for depressive disorder or any other mental disorder in the fifth edition of the DSM (DSM-5) or in the fifth edition, text revision (DSM-5-TR). This isn't because there are fewer people with the symptoms but because NOS is considered an outdated diagnostic category.

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.

However, there are many in the mental health field who disagree with DSM classifications. Some view the DSM's change to certain names of diagnoses as arbitrary (such as the change from NOS to "other specified" or "unspecified").

Some professionals accuse the DSM of oversimplifying, overcomplicating, or misclassifying some disorders. Still, you will find that most mental health professionals in the United States use the DSM at least as a reference to have a basic foundational language for psychiatric diagnoses.

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

'Other Specified' and 'Unspecified'

Changes included the elimination of the catch-all "not otherwise specified" (and NOS) subcategory. The authors 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 the 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 their 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. 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.

5 Sources
Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institute of Mental Health. Depression basics.

  2. American Psychiatric Association. Frequently asked questions about DSM-5 implementation—For clinicians.

  3. Nemeroff CB, Weinberger D, Rutter M, et al. DSM-5: a collection of psychiatrist views on the changes, controversies, and future directionsBMC Med. 2013;11:202. doi:10.1186/1741-7015-11-202

  4. Peele R, Goldstein G, Crowel R. DSM-5: What will it mean to your practice?. Psychiatric Times. 2013;30(10).

  5. Regier DA, Kuhl EA, Kupfer DJ. The DSM-5: Classification and criteria changes. World Psychiatry. 2013;12(2):92-8. doi:10.1002/wps.20050

By Nancy Schimelpfening
Nancy Schimelpfening, MS is the administrator for the non-profit depression support group Depression Sanctuary. Nancy has a lifetime of experience with depression, experiencing firsthand how devastating this illness can be.