Depressive and anxious symptoms and 20-year mortality: Evidence from the Stirling County study

Background: Depression and anxiety disorders are highly comorbid, and share significant symptom overlap. Whereas depression has been consistently associated with excess mortality, the association between anxiety and mortality is less clear. Our aim was to identify constellations of anxious and depressive symptoms and examine their associations with mortality. Method: This study considers respondents from the 1970 (n=1203) and 1992 (n=1402) cohorts of the Stirling County study. Symptoms of depression and anxiety were assessed using structured at-home interviews. Vital status of participants through 2011 was determined using probabilistic linkages to the Canadian Mortality Database. Results: Exploratory factor analysis yielded three correlated factors in each cohort. Items loading on each factor varied slightly between cohorts, but roughly corresponded to (1) depressive symptoms, (2) anxious symptoms, and (3) somatic symptoms. The depressive factor was associated with increased risk of mortality in both the 1970 (HR: 1.35, 95% CI: 1.12, 1.62) and 1992 (HR: 1.25, 95% CI: 1.05, 1.48) cohorts. Anxious symptoms were associated with a reduced risk of mortality in the 1992 sample (HR: 0.72; 95% CI: 0.53, 0.90). Somatic symptoms were associated with a reduced risk of mortality in the 1970 sample (HR: 0.83, 95% CI: 0.69, 0.99), but an elevated risk of mortality in the 1992 sample (HR: 1.29; 95% CI: 1.11, 1.51). Conclusions: This study provides evidence that symptoms of depression and anxiety may have differential associations with early mortality. Somatic symptoms such as upset stomach and loss of appetite may be protective against mortality, perhaps through increased use of health care services. Conversely, symptoms such as weakness and cold sweats may be indicative of failing health.