Depression as a risk factor for breast cancer: investigating methodological limitations in the literature.

PURPOSE

A relationship between depression and the development of breast cancer has not been convincingly shown in the research conducted over the past three decades.

METHODS

In an effort to better understand the conflicting results, a review was conducted focusing on the methodological problems associated with this literature, including time frame between the assessment of depression and the diagnosis of breast cancer and the use of somatic items in measuring depression. Fifteen breast cancer prospective studies were reviewed.

RESULTS

While twelve of the studies found positive associations between depression and breast cancer development, three studies found negative associations. With regard to the predictive associations between depression and breast cancer incidence, the findings revealed that (a) studies using a longer time frame found a stronger association than studies using a shorter time frame and (b) studies utilizing depression measures that did not contain somatic items found a smaller association than studies utilizing depression measures that did contain these items.

CONCLUSIONS

Future studies should ensure that sufficient periods of time between the measurement of depression and the assessment of cancer and avoid measuring depression using somatic items.