Bipolar disorder not otherwise specified (BD-NOS) is a diagnosis for bipolar disorder (BD) when it does not fall within the other established sub-types. Bipolar disorder NOS is sometimes referred to as subthreshold bipolar disorder.
Bipolar disorder is difficult to diagnose. If a person displays some symptoms of bipolar disorder but not others, the clinician may diagnose bipolar NOS. The diagnosis of bipolar NOS is indicated when there is a rapid change (days) between manic and depressive symptoms and can also include recurring episodes of hypomania. Bipolar NOS may be diagnosed when it is difficult to tell whether bipolar is the primary disorder due to another general medical condition, such as substance abuse.