Can psychological interventions increase cancer survival?
The intriguing question of whether participation in a psychosocial group intervention can result in increased survival has been investigated since 1989. The original study  tested a supportive-expressive group therapy format for women with metastatic breast cancer, while another study  tested a psychoeducational group intervention for patients with malignant melanoma. In both of these studies, a survival advantage was found in the intervention group. However, a critique of the first study  found that members of the control group had significantly shorter survival times than would have been expected, when compared with data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) Program, suggesting that the survival advantages may have resulted from inadvertent sampling errors.
Literature reviews, including three meta-analyses [26–28] and one systematic review, have concluded that previous research has failed to find an effect of psychotherapy on survival. One summary  reported on ten additional randomized controlled trials of various psychosocial interventions for patients with various types of cancers (although most were women with breast cancer). All ten studies noted improved psychosocial benefits. However, nine of the ten showed no significant differences in survival, while one  found a survival advantage of about 1 year. This one positive trial was able to stratify groups on a number of important variables (e.g., nodal status, estrogen receptor and progesterone receptor status, and menopausal status) and provided data in support of possible mechanisms such as enhanced immune functioning and patient compliance with stress reduction procedures. In an analysis of results, this study identified the complexity of factors involved in any survival benefit and the possibility that immune system-mediated benefits may contribute to increased survival, when other factors are carefully taken into account.