On what basis may persistent depressive disorder be distinguished from major depression?

The correct answer is the intensity of the symptoms and the duration of the disorder

Persistent depressive disorder (PDD) or dysthymia refers to a persistent and daily depressed mood lasting for at least 2 years. Along with a daily depressed mood, PPD also involves two other symptoms such as increased or decreased appetite, poor memory and concentration, insomnia or hypersomnia, etc.) Major depression on the other hand involves shorter, yet more intense symptoms (or episodes) of depression that last for less than two years.