How does dysthymia differ from depression?

Length and Intensity: Major depression is episodic - it occurs, but gets better. Dysthymia is milder in intensity to a major depressive episode, but lasts much longer (2 years). Both have similar symptoms, but the treatments are a little different since dysthymia responds well to therapy. One can have a major depressive episode in addition to dysthymia.

Low grade but longer: Dysthymia is a mood disorder consisting of chronic depression, with less severe but longer lasting (2 years or more) symptoms than major depressive disorder.

Type of depression: Dysthymia, is a chronic type of depression that doesn't waver all that much in terms of intensity, as opposed to major depression which wavers widely in intensity. Metaphorically speaking, those with dysthymia experience it as having to wear a coat made of lead, 24-7, with little variation. Those with major depression experience the depressive lows almost like waves.