mental illness vs nervous breakdown

mental illness

noun
  • A mental disorder. 

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

nervous breakdown

noun
  • An attack of a psychological disorder such as depression or anxiety so severe that it prevents a person from continuing to function normally 

  • A psychological disorder usually characterized by panic attacks and aggressiveness, related to the Hispanic ataque de nervios. 

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