See the “Differential Diagnosis” section for Major Depressive Disorder. The differential diagnosis between Dysthymic Disorder and Major Depressive Disorder is made particularly difficult by the facts that the two disorders share similar symptoms and that the differences between them in onset, duration, persistence, and severity are not easy to evaluate retrospectively. Usually Major Depressive Disorder consists of one or more discrete Major Depressive Episodes that can be distinguished from the person’s usual functioning, whereas Dysthymic Disorder is characterized by chronic, less severe depressive symptoms that have been present for many years. When Dysthymic Disorder is of many years’ duration, the mood disturbance may not be easily distinguished from the person’s “usual” functioning. If the initial onset of chronic depressive symptoms is of sufficient severity and number to meet full criteria for a Major Depressive Episode, the diagnosis would be Major Depressive Disorder, Chronic (if the full criteria are still met), or Major Depressive Disorder, In Partial Remission (if the full criteria are no longer met). The diagnosis of Dysthymic Disorder can be made following Major Depressive Disorder only if the Dysthymic Disorder was established prior to the first Major Depressive Episode (i.e., no Major Depressive Episodes during the first 2 years of dysthymic symptoms), or if there has been a full remission of the Major Depressive Disorder (i.e., lasting at least 2 months) before the onset of the Dysthymic Disorder.
Depressive symptoms may be a common associated feature of chronic Psychotic Disorders (e.g., Schizoaffective Disorder, Schizophrenia, Delusional Disorder). A separate diagnosis of Dysthymic Disorder is not made if the symptoms occur only during the course of the Psychotic Disorder (including residual phases).
Dysthymic 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 Depressive Features, if the mood disturbance is judged to be the direct physiological consequence of a specific, usually chronic, general medical condition (e.g., multiple sclerosis). 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., Dysthymic Disorder) and the general medical condition is recorded on Axis III (e.g., diabetes mellitus). This would be the case, for example, if the depressive symptoms are considered to be the psychological consequence of having a chronic general medical condition or if there is no etiological relationship between the depressive symptoms and the general medical condition. A Substance-Induced Mood Disorder is distinguished from a Dysthymic Disorder by the fact that a substance (e.g., a drug of abuse, a medication, or exposure to a toxin) is judged to be etiologically related to the mood disturbance.
Often there is evidence of a coexisting personality disturbance. When an individual’s presentation meets the criteria for both Dysthymic Disorder and a Personality Disorder, both diagnoses are given.