Abstract
Breast cancer is the most frequently occurring type of cancer in women in the western world. The etiology of a large proportion of breast cancers is still unexplained, and the possibility that psychosocial factors could play a role is not ruled out. Already in pre-Christian times, it was assumed that psychological factors might play a significant role in the development of breast cancer. However, studies have failed to produce conclusive results. There is still a lack of knowledge on the relationship between breast cancer development and psychosocial factors such as stressful life events, coping styles, depression, and the ability to express emotions. The results of this review show that there is not enough evidence that psychosocial factors like 'ways of coping' or 'non-expression of negative emotions', play a significant role in the etiology of breast cancer.