Timing of depression in relation to risk of ovarian cancer.

Background: Several studies have suggested that depression may be associated with increased risk of ovarian cancer. Less is known about whether timing matters regarding when depression occurs. To provide evidence for an etiologically relevant exposure period, we examined depression occurring during the time in which precursor lesions develop and progress to invasive carcinoma with the risk of developing ovarian cancer.

Methods: Using data from 2 prospective cohorts (1992-2015), we divided follow-up into consecutive 2-year periods for analytic purposes, referred to as "cancer ascertainment periods." We estimated associations of depression in the 10 years before each cancer ascertainment period with incident cancer, using Cox proportional hazards models. Next, we estimated associations of depression occurring up to 18 years before each ascertainment period, in 2-year increments, with incident cancer. We adjusted for demographic, health, and behavioral factors. All tests of statistical significance were two-sided, with a P-value threshold of less than .05.

Results: Depression occurring in the 10 prior years was associated with 30% greater risk of cancer (hazard ratio [HR] = 1.30, 95% confidence interval = 1.15 to 1.46). Associations were similar in fully adjusted models (HR = 1.27). Depression occurring in the 14 years before ascertainment was associated with elevated risk, although only estimates for depression 0-2, 6-8, and 8-10 years before ascertainment reached statistical significance (HR range = 1.20-1.36).

Conclusion: Depression occurring up to 14 years before cancer ascertainment was associated with greater cancer risk. This is the time of precursor progression to invasive ovarian carcinoma, suggesting depression may be an ovarian cancer-promoting agent.