chemically imbalanced vs unsettled

chemically imbalanced

adj
  • Mentally ill. 

  • Used other than figuratively or idiomatically: see chemically, imbalanced. 

unsettled

adj
  • Disturbed, upset. 

  • Unpaid. 

  • Not populated, having no settlers or other inhabitants. 

  • Not in a steady condition, uncertain, subject to change. 

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