Inflammation, Depression and Heart Disease

Sunset in Santa Fe, New Mexico

Major depression appears linked to risk for coronary artery disease and an adverse outcome following myocardial infarction.  The mechanism for this association is unclear.

One proposed mechanism relates to systemic markers of inflammation.  Elevated serum blood levels of inflammatory markers such as interleukin-6 and C-reactive protein are risk factors for heart disease.  Some research point to higher inflammatory markers levels in samples of individuals with depression.

Duivis and colleagues from the Netherlands and the United States recently published an informative study on this issue in the American Journal of Psychiatry.  Their study prospectively examined a series of patients with heart disease with measurements of depression and markers of inflammation.  The key elements of the design of their study included:

Subjects: 667 individuals with documented coronary artery disease interviewed yearly for 5 years
Depression Assessment: 9-item Patient Health Questionnaire corresponding to the 9 items making up the criteria for major depression in DSM-IV.  Subjects were grouped into three categories: never scoring 10 or more on the PHQ, scoring 10 or more at one time, scoring 10 or more at 2 or more interviews
Inflammatory Markers: Fasting blood samples measured for high-sensitivity C-reactive protein (hsCRP), interleukin-6 (IL-6) and fibrinogen.

Subjects with two or more periods with significant depressive symptoms showed statistically higher levels of hsCRP and IL-6 than the other two subject groups (fibrinogen levels showed a trend for higher levels, p=.06)

Subjects with two or more periods with significant depressive symptoms tended to be younger, have a diagnosis of myocardial infarction, use aspirin daily and have lower levels of good (HDL) cholesterol.
They also were more likely to be physically inactive, be a current smoker and have higher levels of obesity (BMI).  This association appeared to occur in only one direction--depression predicted later higher inflammatory markers, high inflammatory markers did not predict subsequent development of depression.

When potential key inflammatory confounding variables were controlled (BMI, smoking and inactivity), the association of depression and higher inflammatory biomarkers washed out.    The authors note that this finding suggests the inflammation linked to depression in heart disease may be amenable to increased efforts to "improve health behaviors".

It is unclear from this study how many subjects received pharmacotherapy or psychotherapy for a diagnosis of depression.  Primary treatment of depression may be necessary to engage and motivate those with depression and heart disease to improve their lifestyle choices and behaviors.

Photo of sunset in Santa Fe, New Mexico from the author's collection.

Duivis, H., de Jonge, P., Penninx, B., Na, B., Cohen, B., & Whooley, M. (2011). Depressive Symptoms, Health Behaviors, and Subsequent Inflammation in Patients With Coronary Heart Disease: Prospective Findings From the Heart and Soul Study American Journal of Psychiatry, 168 (9), 913-920 DOI: 10.1176/appi.ajp.2011.10081163