Dysthymia is
Persistent mood disorders are characterised by persistent mood symptoms which last for more than 2 years but are not severe enough to be labelled as even hypomania or mild depressive episode. If the symptom consists of persistent mild depression, the disorder is called as dysthymia (Ref: A sho textbook of psychiatry, Niraj Ahuja,7th edition, pg no73)
Chronic mild depression
Chronic severe depression
Bipolar disorder
Personality disorder
Mood disorders