Why do some people call psychologists 'shrinks'?

The term "shrink" to refer to psychologists supposedly was coined by author Thomas Pynchon in his book The Crying of Lot 49 published in 1966. Most likely it came from the term "headshrinker," comparing the process of psychotherapy to primitive tribal practices of shrinking the heads of enemies. One of the symptoms of SEVERE depression is a sensation of pressure inside the skull- like your brain is swollen. After experiencing this once, patients are vigilant for early warning signs of depression and seek treatment before symptoms progress to severe. Psychiatrists were the original headshrinkers. Later shortened to shrinks.