How can dysthymia be diagnosed?

Dysthymia: Chronic depression with less severe but longer lasting symptoms than major depression. It persists for at least 2 years. It shows anhedonia, low drive & interests, low self-esteem, withdrawal & avoidance.

Dysthymia: 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.