Breast cancer is one of the major causes of premature mortality in women. Research suggests that psychological stress may be a contributing factor to breast cancer development. However, the molecular mechanisms responsible for such an association have yet to be clearly defined. This research work outlines the current state of knowledge on the relationship between stress and breast cancer and focuses on identifying novel molecular signals which may contribute to the effect of stress on breast physiology. With the help of molecular techniques, The Breast Cancer Susceptibility Gene 1 (BRCA1), an important regulator of the genetic processes responsible for tumor development, is identified as a target of stress signalling. In addition, the currently unknown role of genetic modifiers in the relationship between stress and breast cancer is addressed through the development of an epidemiological study examining if stress- susceptible individuals are at an increased risk of developing breast cancer. An integrative model, incorporating genetic stress susceptibility and downstream changes in the expression and activity of molecular regulators is proposed.