Researchers from the University of Pittsburgh evaluated 611 women who had undergone total or partial mastectomy and were treated with chemotherapy, radiation and/or hormone therapy. Their objective was to determine which factors — demographics, tumor size, pain severity, treatments, stress, and psychological factors — contribute to postmastectomy pain.
According to the authors, previous research has provided little consensus regarding the most important determinants of pain following mastectomy. Earlier studies had small sample sizes and focused on just one group of variables. For this research, the authors used a much larger sample, which allowed them to study a large number of variables at the same time.
Results showed, in accordance with some previous research, that there was no evidence of linkage between the type of mastectomy performed, tumor size, or the occurrence of treatment side effects and the development of postmastectomy pain. However, psychosocial variables were found to be important predictors. Specifically, anxiety, depression, impaired sleep, somatization and catastrophizing each were independently related to the development of persistent postmastectomy pain.
source : http://www.sciencedaily.com/releases/2013/11/131106113908.htm