What does double depression means?

Ans. C. Depression superimposed on dysthymiaDouble depression refers to the co-existence of major depressive disorder (MDD) and persistent depressive disorder (PDD), (the latter was previously referred to as dysthymia). Research has shown that double depression tends to be more severe than either MDD or PDD alone and that individuals with double depression experience relapse more often than those with either MDD or PDD alone. However, there is some research that indicates few differences exist between double depression, MDD, and PDD; as a result, those researchers conclude that double depression is not a distinct disorder.