dysthymia vs moodiness

dysthymia

noun
  • A tendency to be depressed, without hope. 

  • A form of clinical depression, characterized by low-grade depression which lasts at least 2 years. 

moodiness

noun
  • The property of being moody. 

How often have the words dysthymia and moodiness occurred in a corpus of books? (source: Google Ngram Viewer )