depression vs pessimism

depression

noun
  • A state of mind producing serious, long-term lowering of enjoyment of life or inability to visualize a happy future. 

  • Four consecutive quarters of negative, real GDP growth. See NBER. 

  • A lowering, in particular a reduction in a particular biological variable or the function of an organ, in contrast to elevation. 

  • A period of major economic contraction. 

  • The act of lowering or pressing something down. 

  • A period of low morale or unhappiness (a period of experiencing the above-mentioned state of mind) which lasts longer than several weeks and may include ideation of self-inflicted injury or suicide. 

  • An area that is lower in topography than its surroundings. 

  • An area of lowered air pressure that generally brings moist weather, sometimes promoting hurricanes and tornadoes. 

pessimism

noun
  • The condition of being pessimal. 

  • A general belief that bad things will happen. 

  • The doctrine that this world is the worst of all possible worlds. 

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