Can you tell me what is dysthymic disorder?

Chronic depression. Dysthymic disorder is a form of chronic depression lasting more than 2 years which is generally mild-moderate in severity (less severe than major depression). Symptoms associated with dysthymic disorder include all the symptoms that could be involved in major depression, including sleep, appetite or concentration disturbances, suicidal ideation, loss of interest in things, guilt, etc.
Mild depression. More severe are depression - mania - bipolar disorder less severe are dysthymia - hypomania - cyclothymia the crux of the difference is the degree to which the mood disorder interferes with one's activities of daily living.