Depressive disorder is well known to be associated with increased mortality. Few previous studies have shown that presence of depressive symptoms ( not meeting the threshold for diagnosis of depression) is associated with increased mortality.
White and colleagues from UK looked at the association of mortality with depressive symptoms across full range of severity. ELSA (English longitudinal study of ageing) is on ongoing longitudinal ,prospective cohort study started in 2002. This is a nationally representative sample of participants with age 50 or more . Participants were interviewed to assess depressive symptoms on the 8 item CES-D ( Centre for Epidemiological Studies) scale. Social ( e.g.socio economic class) , life style ( e.g. physical activity), clinical ( e.g. all physical health disorders ) and demographic information were also available. Mortality data for 9 year period was used to study the association.
60% of people reported at least one depressive symptom.People reporting a greater severity of depressive symptoms were more likely to be female, older, non-white, have lower wealth,live alone, have impaired physical functioning, a smoker,hardly ever engage in physical activity, use antidepressants, and report a doctor-diagnosed health condition than those with lower scores. 20% died during the 9 yr period.
Relative to study members with no symptoms, an increased risk of mortality was found in people with depressive symptoms. Socio economic position, physical disorders, heath behaviours, functional impairements- all contributed to the observed association between depressive symptoms and mortality. Physical activity and functional impairments alone accounted for 73% of the depressive symptom mortality association.
It can be that depressive symptoms lead to inactivity and functional impairment and this lead to increased mortality ( = Meditational Association) . It is also possible that inactivity and functional impairments lead to depressive symptoms as well as increased mortality ( = Confounding Assn). The third possibility is depressive symptoms exerting a direct physiological effect ( e.g. immune mediated) that increase mortality (= direct effect).
Limitations: CES-D cannot generate diagnosis of depression. The tool ask for the presence of depressive symptoms for one week only.
Conclusions: The study shows that there is an association between depressive symptoms and mortality. This association exist across all severity range.
Comments: Depressive symptoms are clinically important indicator of increased mortality. Clinical and social factors may explain the links. Clinicians need to look at any depressive symptoms closely to identify potential, modifiable factors and offer interventions.
Summary of the article:
White J, Zaninotto P, Walters K, Kivimäki M, Demakakos P, Shankar A, Kumari M, Gallacher J, Batty GD.
Psychol Med. 2015 Oct;45(13):2771-9.