cynanthropy vs mental illness

cynanthropy

noun
  • A delusion in which a person believes he or she is transformed into a dog. 

  • A shape-shifting ability between human and canine forms. 

mental illness

noun
  • A mental disorder. 

  • The property of being mentally ill; mental disorders taken as a whole. 

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