Regular paper
Clinical depression and inflammatory risk markers for coronary heart disease

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Abstract

Despite mounting evidence that psychiatric depression heightens risk for cardiac morbidity and mortality, little is known about the mechanisms responsible for this association. The present study examined the relation between depression and the expression of inflammatory risk markers implicated in the pathogenesis of coronary heart disease (CHD). One hundred adults were enrolled (68% women, 48% Caucasian, 48% African-American, mean age 30 ± 2 years). Fifty subjects met the diagnostic criteria for clinical depression; the remaining 50 were demographically matched controls with no history of psychiatric illness. All subjects were in excellent health, defined as having no acute infectious disease, chronic medical illness, or regular medication regimen aside from oral contraceptives. The depressed subjects exhibited significantly higher levels of the inflammatory markers C-reactive protein (3.5 ± 0.5 vs 2.5 ± 5 mg/L, p = 0.04) and interleukin-6 (3.0 ± 0.3 vs 1.9 ± 0.2 pg/ml, p = 0.007) compared with control subjects. Mediational analyses aimed at identifying the pathways contributing to this association revealed that neither cigarette smoking nor subclinical infection with cytomegalovirus or Chlamydia pneumoniae had been responsible. However, depressed subjects exhibited greater body mass than control subjects, and analyses were consistent with adiposity accounting for a portion of the relation between clinical depression and increased expression of inflammatory markers. These findings indicate that in otherwise healthy adults, depression is associated with heightened expression of inflammatory markers implicated in the pathogenesis of CHD. Increased body mass appears to be partially, although not completely, responsible for this relation.

Section snippets

Subjects:

A total of 100 adults were enrolled in the study; 50 of them met the diagnostic criteria for clinical depression, and the remaining 50 had no history of psychiatric illness. The groups were matched on a case-by-case basis with respect to age, gender, and ethnicity. All subjects were in good health, defined as having no history of chronic medical illness, no indications of acute infectious disease at study entry, as evidenced by a normal complete blood count, and no prescribed medication regimen

Results

Depressed and control subjects were very similar with respect to demographic features and cardiovascular risk factors (Table 1). The only exception to this was weight; depressed subjects weighed significantly more than controls (F [1, 98] = 6.84, p <0.01).

Discussion

The present study shows that in otherwise healthy adults, depression is accompanied by elevated levels of 2 inflammatory risk markers that have been implicated in CHD pathogenesis.10, 11, 20 These elevations are fairly large; on average, subjects with depression exhibited 41% higher CRP levels and 54% higher interleukin-6 levels than control subjects. Although an association between depression and inflammation has been reported,21, 22, 23, 24, 25 our study extends these findings by assessing

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    This study was supported by a Grant-In-Aid from the American Heart Association, Dallas, Texas and a Veterans Administration Merit Review, St. Louis, Missouri.

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