Effect of neuroticism on risk of cardiovascular disease in depressed persons - a Swedish population-based cohort study

Background: The relationship between neuroticism, depression and cardiovascular disease (CVD) is complex and has so far not been studied in depth. The aim of this study was to determine if neuroticism is an effect-modifier in the association between depression and CVD. Data derived from a longitudinal cohort study on mental health, work and relations among adults (20-64 years), including 10,443 individuals. Depression was assessed using the Major Depression Inventory (MDI) and neuroticism by the Swedish Scale of Personality (SSP). Outcomes of cardiovascular disease were register-based from the National inpatient register. Results: Both depression (OR 1.9 (95%CI 1.4, 2.5)) and high levels of neuroticism (OR 1.2 (95%CI 1.1-1.3)) were associated with increased risk of CVD. The combined effect of depression and neuroticism on the risk of CVD revealed HRs ranging from 1.0 to 1.9 after adjusting for age and gender, socioeconomic position, prevalent hypertension and diabetes. Almost similar associations were seen after further adjustment for lifestyle factors. Conclusion: Neuroticism increased the risk of CVD in depressed persons. We found synergistic interaction between neuroticism and depression status in predicting future risk of CVD.