Psychiatrically-diagnosed depression and subsequent cancer

In a follow-up of up to 19 years, 923 patients with some form of depression diagnosed in a psychiatry clinic showed a slightly elevated risk of developing cancer in comparison with the other members of a cohort of 143,574 persons who received prescriptions from a pharmacy (Standardized morbidity ratio, 1.21; 95% confidence interval 0.95-1.53). When cancers diagnosed in the first 2 years after the diagnosis of depression were ignored, the risk increased somewhat (Standard morbidity ratio, 1.38; 95% confidence interval, 1.06-1.76). A subgroup of these depressed patients who had multiphasic health checkups were more apt to be of white race, unmarried, and users of postmenopausal estrogens if females than a matched comparison group of multiphasic examinees. These differences probably explain much of the group's excess cancers, most of which were located in the breast, endometrium, and skin (both melanoma and nonmelanoma). This study lends little if any support to the hypothesis that depression predisposes to cancer occurrence.