Loss of a parent and the risk of cancer in early life: A nationwide cohort study

Background: While early-life exposure to stress has been associated with subsequent psychiatric and cardiovascular morbidity, little is known regarding its potential role in cancer development. We hypothesized that severe emotional stress, such as the loss of a parent through death during childhood, may increase the risk of cancer in early life. Method: Based on the Swedish Multi-Generation Register, we identified a cohort of 4,219,691 individuals who had both parents identifiable in the same register and followed the cohort from birth to the age of 40 years between 1961 and 2006. Through information retrieved from the Swedish Causes of Death and Cancer Registers, we ascertained death among the parents and cancer diagnosis among the cohort individuals. We used Poisson regression to calculate the relative risks (RRs) and 95 % confidence intervals (CIs). Results: Parental death was not associated with total cancer risk. However, parental death during childhood was associated with a higher risk of human papillomavirus (HPV) infection-related cancers (RR 1.4; 95 % CI 1.2-1.7), and loss during early adulthood (>18 years) entailed a higher risk of cancers of the stomach (RR 1.8; 95 % CI 1.3-2.6), lung (RR 1.7; 95 % CI 1.1-2.4), rectum (RR 1.4; 95 % CI 1.0-2.0), and breast (RR 1.1; 95 % CI 1.0-1.3). A significant association was observed for pancreatic cancer for both loss during childhood (RR 2.6; 95 % CI 1.6-4.2) and afterward (RR 2.8; 95 % CI 1.9-4.3). Conclusion: Our results suggest that severe psychological stress in early life may be associated with premature development of certain malignancies, particularly cancers related to smoking and HPV infection.