In a large prospective study by research psychologist Richard Shekelle and his team at the Western Electric plant in Chicago, 2,010 middle-aged male employees were given psychological tests that looked specifically at depression scores. The men were followed for seventeen years. The men who had tested as depressed developed cancers over the course of the next seventeen years at double the rate of those who were shown in the initial tests to not be depressed.
In a different study, research psychologist Richard Schultz found that during the course of an eight-month time span, patients with recurrent cancers between the ages of 30 and 59 who were pessimistic had significantly greater mortality rates than those with the same prognosis who were more optimistic.
Based on these and many similar studies, it is now clear that any method of psychotherapy, meditation, the cultivation of environmental mastery,
or any other method that leads to a happier outlook on life may simultaneously reduce the odds of contracting cancer.