Cyclothymic Disorder must be distinguished from a Mood Disorder Due to a General Medical Condition. The diagnosis is Mood Disorder Due to a General Medical Condition, With Mixed Features, when the mood disturbance is judged to be the direct physiological consequence of a specific, usually chronic general medical condition (e.g., hyperthyroidism). This determination is based on the history, laboratory findings, or physical examination. If it is judged that the depressive symptoms are not the direct physiological consequence of the general medical condition, then the primary Mood Disorder is recorded on Axis I (e.g., Cyclothymic Disorder) and the general medical condition is recorded on Axis III. This would be the case, for example, if the mood symptoms are considered to be the psychological consequence of having a chronic general medical condition or if there is no etiological relationship between the mood symptoms and the general medical condition.
A Substance-Induced Mood Disorder is distinguished from Cyclothymic Disorder by the fact that a substance (especially stimulants) is judged to be etiologically related to the mood disturbance. The frequent mood swings that are suggestive of Cyclothymic Disorder usually dissipate following cessation of drug use.
Bipolar I Disorder, With Rapid Cycling, and Bipolar II Disorder, With Rapid Cycling, both may resemble Cyclothymic Disorder by virtue of the frequent marked shifts in mood. By definition, the mood states in Cyclothymic Disorder do not meet the full criteria for a Major Depressive, Manic, or Mixed Episode, whereas the specifier With Rapid Cycling requires that full mood episodes be present. If a Major Depressive, Manic, or Mixed Episode occurs during the course of an established Cyclothymic Disorder, the diagnosis of either Bipolar I Disorder (for a Manic or Mixed Episode) or Bipolar II Disorder (for a Major Depressive Episode) is given along with the diagnosis of Cyclothymic Disorder.
Borderline Personality Disorder is associated with marked shifts in mood that may suggest Cyclothymic Disorder. If the criteria are met for each disorder, both Borderline Personality Disorder and Cyclothymic Disorder may be diagnosed.