Historical and nosological aspects of dysthymia.

From the time of Hippocrates, the problem of persistently depressed mood has been recognised clinically. The first modern description of dysthymia was by Kahlbaum, who distinguished it from the fluctuating mood of cyclothymia. However, there has been continuous difficulty in separating low-grade depressive disorder from an abnormal personality trait. DSM-II defined chronic depression as a personality disorder, but Akiskal subsequently reclassified it as a mood disorder. In DSM-III, all chronic depression lasting more than two years was defined as 'Dysthymic disorder'. DSM-III-R brought together dysthymic and cyclothymic disorders into an affective category. ICD-10 dysthymia subsumes a number of categories which include recurrent depression of mood. The primary distinction between Dysthymia and Major Depressive Disorder is that Dysthymia is chronic, but symptomatically less severe. A number of unresolved problems remain in relation to its nosological status.