Dysthymia Is a Specific Type of Depressive Disorder, Differentiated from Major

Dysthymia is a specific type of depressive disorder, differentiated from major depression disorder by a number of features. Which of the following differentiations between these two disorders is NOT valid?

A) Dysthymia often lasts longer than major depression.
B) Someone with dysthymia is likely to develop major depression.
C) Someone with major depression is likely to develop dysthymia.
D) More than half of those diagnosed with dysthymia have a comorbid psychiatric disorder or chronic physical illness.