Confirmatory bias and the persistent influence of discredited data in interpreting the stress-cancer link: commentary on Michael et al. (2009)

Comments on the original article, "Influence of stressors on breast cancer incidence in the Women's Health Initiative" by Y. L. Michael et al (see record 2009-03297-001). The current authors assert that Michael et al (2009) missed an opportunity for a straightforward reporting of null findings concerning the association between stress and incidence of cancer. They urge greater skepticism toward the claims about a stress-cancer link more generally. Using data from the Women's Health Initiative, Michael and colleagues suggested an association between stress and the incidence of breast cancer. However, the current authors believe their results and those from other studies failed to confirm that stress is a risk factor of breast cancer. Starting with their abstract and continuing in their discussion, Michael et al selectively and inaccurately reported findings with a strong confirmatory bias, and with further selective and uncritical reference to the existing literature. Moreover, they inadvertently perpetuated the direct and indirect influence of discredited data in the literature purporting to show a stress-cancer link.