Not Otherwise Specified (NOS)

What Does It Mean?

Not Otherwise Specified (NOS)
Credit: PEDRE/Getty Images

Definition: NOS is an abbreviation for the term "Not Otherwise Specified" which is used when making diagnoses under the Diagnostic and Statistical Manual of Mental Disorders.  Under the fourth edition of this manual, NOS was used as a broad-based diagnostic category, for instance "Depressive Disorder NOS. " The choice of the NOS diagnosis meant that the diagnosing doctor believed that the patient's problems fell into a particular family of disorders (e.g., depressive disorders, anxiety disorders, etc.) but that there was not enough information at the time of diagnosis to better specify the type of disorder.

A person with Depressive Disorder NOS would have had several symptoms seeming to indicate a particular disorder, such as Major Depressive Disorder; however, the criteria for this disorder would not be met fully enough for the person to qualify for diagnosis with that disorder. 

The term "Not Otherwise Specified" was done away with in the latest edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and replaced with the terms "Other Specified" and "Unspecified."   "Other Specified" and "Unspecified" are both used to indicate clusters of symptoms which do not neatly fit into another existing category.  The difference between the two lies in whether the clinician 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.  "Unspecified" might be used in a situation such as an emergency room where there is insufficient information to make a more specific diagnosis, but with the potential for a specific diagnosis to be made at some future time when more information becomes available.

According to the American Psychiatric Association, the author of the DSM-5, the designation of "Unspecified" allows doctors to provide their patients with the best possible care in situations, such as in the emergency room, when a full diagnosis may not be possible, but treatment is nevertheless needed.

  The treating physician is able to be as specific as possible in his diagnosis without necessarily showing that a patient meets the full criteria for a given diagnosis.

The APA further notes that these changes bring the DSM-5 more in alignment with the World Health Organization's International Classification of Diseases, which requires mandatory codes for disorders which do not precisely fit current definitions for major disorders. 

The DSM-5 further requires that the person must be experiencing clinically significant impairment and distress in important aspects of his life, such as at home and at work, in order to receive this diagnosis.  This requirement ensures that the clinician can make an appropriate diagnosis of a patient's condition.


"Frequently Asked Questions About DSM-5 Implementation - For Clinicians."  American Psychiatric Association DSM-5 Development.  American Psychiatric Association.  Updated:  October 7, 2014.  Accessed:  January 13, 2016.

Peele, Roger, Gustavo Goldstein and Raymond Crowel.  "DSM-5:  What Will It Mean to Your Practice?"  Psychiatric Times.  UBM Medica, LLC.  Published:  October 10, 2013.  Accessed:  January 13, 2016.

Continue Reading