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Biol Psychiatry. 2010 Dec 1;68(11):999-1006. doi: 10.1016/j.biopsych.2010.07.033. Epub 2010 Oct 15.

Sustained elevation of serum interleukin-6 and relative insensitivity to hydrocortisone differentiates posttraumatic stress disorder with and without depression.

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  • 1National Institutes of Nursing Research, Bethesda, Maryland, USA.

Abstract

BACKGROUND:

Elevated levels of proinflammatory cytokines, especially interleukin-6 (IL-6), can mediate the greater risk for cardiovascular disease in individuals with posttraumatic stress disorder (PTSD), particularly in those with comorbid major depressive disorder (MDD). However, IL-6 levels are not consistently elevated in either PTSD or MDD. Although PTSD is associated with supersensitivity to glucocorticoids; prior studies have not evaluated the effect of comorbid MDD.

METHODS:

Serum IL-6 levels were measured hourly between 7:00 pm and 7:00 am in individuals with PTSD with comorbid MDD (PTSD + MDD) (n = 9) and compared with those with PTSD without MDD (PTSD - MDD) (n = 9) and nontraumatized healthy control subjects (n = 14). Group differences in serum IL-6, plasma adrenocorticotropic hormone (ACTH), and plasma cortisol response to 30 mg of intravenous hydrocortisone were evaluated using linear mixed models.

RESULTS:

Only subjects with PTSD + MDD exhibited higher, overnight serum IL-6 levels compared with individuals with PTSD - MDD (p < .01) and healthy control subjects (p < .001). Peak overnight IL-6 levels positively correlated with severity of PTSD (r = .56, p < .01) and depressive symptoms (r = .54, p < .01). Hydrocortisone administration significantly reduced IL-6 levels in both PTSD groups; however, IL-6 levels in PTSD + MDD were higher than both PTSD - MDD (p < .05) and healthy control subjects (p < .01). Following hydrocortisone administration, there was a greater reduction in levels of ACTH in PTSD - MDD compared with control subjects (p < .01).

CONCLUSIONS:

Sustained elevations of overnight IL-6 levels and relatively decreased sensitivity to hydrocortisone distinguish PTSD + MDD from PTSD - MDD. Novel strategies that decrease IL-6 levels offer a new direction in the prevention and treatment of PTSD and associated comorbid medical illnesses.

Copyright © 2010. Published by Elsevier Inc.

PMID:
20951370
[PubMed - indexed for MEDLINE]
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