The researchers say women exposed to negative life events have an increased risk of breast cancer.

For the new study the researchers interviewed 622 women between the ages of 25 and 45, of the group 255 were breast cancer patients and 367 were healthy women.

The women answered questions about their life experiences and evaluated their levels of happiness, optimism, anxiety, and depression prior to diagnosis; this information was then examined and the relationship between life events, psychological distress and breast cancer among young women, correlated.

According to the researchers from the Ben-Gurion University of the Negev, the results showed a clear link between outlook and risk of breast cancer, with optimists 25 percent less likely to have developed the disease.

Professor Ronit Peled, says women who suffered two or more traumatic events had a 62 percent greater risk, and young women exposed to a number of negative life events should be considered an 'at-risk' group for breast cancer and should be treated accordingly.

The researchers say that experiencing more than one severe and/or mild to moderate life event is a risk factor for breast cancer among young women, but a general feeling of happiness and optimism can play a protective role and a generally positive outlook appears to reduce the chance of breast cancer by a quarter.

Professor Peled, says the mechanism in which the central nervous, hormonal and immune systems interact and how behaviour and external events modulate these three systems is not fully understood.

Professor Peled suggests that the relationship between happiness and health should be examined in future studies and relevant preventative initiatives should be developed.

The study "Breast Cancer, Psychological Distress and Life Events among Young Women," is published in the British journal BMC Cancer.

How can one reconcile these interesting research findings in animals with the lack of antidepressant efficacy of a CRF1 receptor antagonist in the Pfizer study? Is this approach simply ineffective in humans or might there be subgroups of patients who might be more likely to respond to a CRF1 antagonist? The Surget et al. data raise the possibility that CRF1 receptor antagonists might be effective in treating stress-related behavioral disturbances even in a context where other antidepressants do not work, perhaps due to disruption of neurogenesis. John H. Krystal, M.D., Editor of Biological Psychiatry and affiliated with both Yale University School of Medicine and the VA Connecticut Healthcare System, comments: "These findings lend weight to the hope that CRF1 antagonists might play a role in the treatment of antidepressant-resistant symptoms of depression or posttraumatic stress disorder. If so, CRF1 antagonists could fulfill an important unmet need." He adds that "we do not need another Prozac, but we urgently need to find ways to help the large number of patients who fail to respond adequately to our available treatments."