Despite Differences Among Epidemiological Surveys in Samples, Methods, and Definitions

Despite differences among epidemiological surveys in samples, methods, and definitions of mental disorders, what is one common finding concerning mood disorders?

A) Bipolar disorder occurs in fewer people than major depressive disorder.
B) Dysthymic disorder is the most common form of mood disorder.
C) Mood disorders are the most common form of mental disorders.
D) Bipolar and unipolar disorders are equally common in the general population.