New cases of cancerwere identified from Medicare hospitalization records and death certificates.
Of the 4825 persons studied, 146 (3.0%) were chronicallydepressed.
All previous prospective studies used a single measurement occasion to assess depressed mood.
However, any hypothesis linking depression and later development of cancer presumably implies some element of chronic mental illness.
Symptoms of depression were assessed in the interviews at baseline (1988) and 3 years (1985) and 6 years (1982) before baseline with the use of the Center for Epidemiologic Studies-Depression (CES-D) scale .
Chronically depressed mood was defined as present when the number of depressive symptoms exceeded specific cut points on the Center for Epidemiologic Studies-Depression scale at baseline (1988) and 3 and 6 years before baseline.
The scores of these shorter versions were transformed by use of the procedure recommended by Kohout et al. Briefly, for men and women separately, the scores from East Boston and Iowa were standardized against the 1974–1975 National Health and Nutrition Examination Survey (NHANES I), by means of the equation , in parentheses) of CES-D scores from NHANES I for men and women were, respectively, 7.1 (7.2) and 10.0 (9.1).
Full details on the use of the modified scales, the methods for transforming the results to accord with the full scale, and the validity of these scales have been published .
This makes the overall interpretation of their findings complicated, since results could be attributed to the fact that, among smokers, depression is associated with specific patterns of smoking behavior that increase the risk of cancer.
For example, it has been proposed that depressed smokers inhale moredeeply and are less likely to quit than nondepressed smokers (16–18).