How does depression lead to cardiovascular adverse events?

exercise depression

Depression is recognized as a risk factor for the development of cardiovascular disease in healthy patients, for recurrent events in patients with established cardiovascular disease, and for adverse outcomes after coronary bypass graft surgery. Physical inactivity largely explains the association between depressive symptoms and adverse cardiovascular events such as heart failure, myocardial infarction, stroke, transient ischemic attack, or death.

Other possible explanatory factors for the association of depression with cardiovascular disease are:

  • smoking
  • lack of exercise
  • medication non adherence
  • worse underlying cardiac disease severity
  • lower heart rate variability
  • antidepressant toxicity
  • enhanced activity of the hypothalamic pituitary axis
  • greater catecholamine levels
  • dietary factors,low omega-3fatty acid levels
  • increased serotonin and platelet activation
  • inflammatory processes

In a recent study published in a recent number of the JAMA this result was published. This publication is about a prospective cohort of 1017 participants with stable coronary disease. They evaluated the extent to which the association of depressive symptoms with subsequent cardiovascular events was explained by differences in comorbid conditions, cardiac disease severity, use of antidepressant medications, and potential biological and behavioral mediators.

Even when they adjusted for confounding factors, factors that could also mediate the influence on adverse cardiovascular events such as comorbid conditions and cardiac disease severity, depressive symptoms remained associated with a 31% increased rate of cardiovascular events.

However, no significant association between depressive symptoms and cardiovascular events remained after adjustment for physical activity and other health behaviors.

This means that it is possible that the increased risk of cardiovascular events associated with depression could potentially be preventable with behavior modification, especially exercise.
This important question whether exercise can decrease the excess risk of cardiovascular events associated with depressive symptoms has not been studied yet. It is possible that the combination of exercise and antidepressants can reduce the risk of cardiovascular events in patients with depression.

This study does not solve the direction of the relationship between physical activity and depression.

the association is almost certainly bidirectional because depression leads to physical inactivity, and physical inactivity exacerbates depression. This can result in a downward spiral in which depression and physical inactivity become mutually reinforcing.

Nevertheless inactivity appeared to account for almost half of the association between depressive symptoms and cardiovascular events in this study. This raises the possibility that increased exercise may decrease the risk of cardiovascular events associated with depression. What do you think?
M. A. Whooley, P. de Jonge, E. Vittinghoff, C. Otte, R. Moos, R. M. Carney, S. Ali, S. Dowray, B. Na, M. D. Feldman, N. B. Schiller, W. S. Browner (2008). Depressive Symptoms, Health Behaviors, and Risk of Cardiovascular Events in Patients With Coronary Heart Disease JAMA: The Journal of the American Medical Association, 300 (20), 2379-2388 DOI: 10.1001/jama.2008.711