Increased risk for depression after breast cancer: A nationwide population-based cohort study of associated factors in Denmark, 1998-2011

Purpose: To investigate the risk for first depression, assessed as incident hospital contacts for depression and incident use of antidepressants, among women with breast cancer. Patients and Methods: Danish national registries were used to identify 1,997,669 women with no diagnosis of cancer or a major psychiatric disorder. This cohort was followed from 1998 to 2011 for a diagnosis of breast cancer and for the two outcomes, hospital contact for depression and redeemed prescriptions for antidepressants. Rate ratios for incident hospital contacts for depression and incident use of antidepressants were estimated with Poisson regression models. Multivariable Cox regression was used to evaluate factors associated with the two outcomes among patients with breast cancer. Results: We identified 44,494 women with breast cancer. In the first year after diagnosis, the rate ratio for a hospital contact for depression was 1.70 (95% CI 1.41 to 2.05) and that for use of antidepressants was 3.09 (95% CI 2.95 to 3.22); these rate ratios were significantly increased after 3 and 8 years, respectively. Comorbidity, node-positive disease, older age, basic and vocational educational levels, and living alone were associated with use of antidepressants. Conclusion: Women with breast cancer are at long-term increased risk for first depression, including both severe episodes leading to hospital contact and use of antidepressants. Clinicians should be aware that the risk is highest in women with comorbid conditions, node-positive disease, and age of 70 years or more. We found no clear association between type of surgery or adjuvant treatment and risk for depression.