Drs. James H. Stephenson and William J. Grace of New York Hospital compared 100 women with cancer of the cervix and 100 with cancer not involving the reproductive system. They found that sexual adjustment among the cervix cancer victims had been poor long before they developed the disease: They had had less intercourse than the others and rarely enjoyed orgasm. In many cases there was actual aversion for the sexual act.
In The Breast Journal, an Essay on Sexual Frustration as the Cause of Breast Cancer in Women: How Correlations and Cultural Blind Spots Conceal Causal Effects has as its main thesis that breast cancer is essentially caused by sexual frustration and dissatisfaction. These are not the common causes that the Mayo Clinic had in mind.
We already know that depressed people suffer higher rates of cancer for they die more frequently from it than their happier peers. This is just basic commonsense backed by clinical reality. One large-scale study among approximately 2,000 middle-aged male employees of the Western Electric Company reported that those individuals who were more depressed were 2.3 times as likely to die of cancer during the following 17 years than their non-depressed counterparts.
 Life Stress and Cancer of the Cervix. JAMES H. STEPHENSON, M.D., and WILLIAM J. GRACE, M.D. http://www.psychosomaticmedicine.org/cgi/reprint/16/4/287.pdf
 Stress, Emotions, and Câncer. University of Iowa. http://www.uihealthcare.com/topics/medicaldepartments/cancercenter/prevention/preventionstress.html