Blood Test for Suicide Risk?

Deborah Brauser

April 26, 2013

Suicidal thoughts and behavior may be uniquely linked to inflammatory markers in patients with major depressive disorder (MDD), new research suggests.

A study of 122 adults in Ireland showed that those with MDD and high suicidal ideation had significantly higher levels of inflammation (as shown through blood draws) than both those with MDD and low suicidal ideation and healthy peers without MDD.

In addition, inflammatory index scores did not differ significantly between the latter 2 groups.

"This suggests that inflammatory molecules may be playing a role in suicidal ideation," lead author Aoife O'Donovan, PhD, adjunct assistant professor of psychiatry at the University of California, San Francisco, told Medscape Medical News.

"However, there's another side to this because we know that psychological stress can increase levels of these molecules. So it could be that feeling suicidal is activating a stress response and promoting the production of these cytokines," said Dr. O'Donovan, who was at the School of Medicine and Medical Sciences at University College Dublin in Ireland at the time of this study.

Still, "the findings suggest that further research on inflammation as a contributor to the pathophysiology of suicidal depression is warranted and could even yield novel adjunct treatments for MDD," write the investigators.

The study was published in the April issue of Depression and Anxiety.

Inflammatory Markers

Dr. Aoife O'Donovan

A total of 122 participants were enrolled at 2 hospitals in Dublin. Of these, 74 were inpatients with MDD (29 with high suicidal ideation and 45 with low suicidal ideation) and 48 were healthy volunteers who did not have MDD (control group).

Measures administered included the Hamilton Rating Scale for Depression to assess depression severity and the Mini–International Neuropsychiatric Instrument to determine level of suicidal ideation.

Fasting blood samples were drawn from all participants to measure inflammatory markers.

A composite score comprising the proinflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor–alpha (TNF-α), the anti-inflammatory cytokine interleukin-10 (IL-10), and C-reactive protein (CRP) was used as an inflammatory index.

"The underlying model for this paper was to gain a better understanding of how these molecules are acting in major depression," said Dr. O'Donovan.

Circulating levels of adrenocorticotropic hormone (ACTH) and cortisol were also measured to assess hypothalamic-pituitary-adrenal (HPA) axis abnormalities.

Treatment Implications?

Results showed higher inflammatory index scores for the group with MDD and high suicidal ideation compared with the group with MDD and low suicidal ideation (P = .009) and compared with the control group (P < .001).

The high suicidal ideation group also showed significantly higher levels of IL-6 and CRP compared with the healthy control participants (P < .001 and P = .01, respectively) and compared with the low suicidal ideation group (P = .02 for both markers).

Neither the inflammatory index composite scores nor any of the individual inflammatory markers differed significantly between the group with MDD and low suicidal ideation and the control group.

"Follow-up analyses indicated that differences between patients with MDD and high versus lower suicidal ideation were independent of depression severity and recent suicide attempts," write the researchers.

There were no significant differences between any of the groups on ACTH or cortisol levels.

Despite the strong association between suicidal ideation and inflammation in patients with MDD, the investigators note that "it is difficult to draw any conclusions about specificity in the relationship."

"Because these cytokines are involved in a lot of different symptoms, it's unlikely that this can prove to be a very specific marker of suicidal ideation. What's more likely is that this might give us an insight into treatments for people who feel suicidal," added Dr. O'Donovan.

"It might also be useful as part of a battery of biological tests that are used to identify people who are suicidal. But it will take quite a bit of time for that to be developed."

The study was funded by the Craig Dobbin Newman Scholarship in Mental Health Research, Society in Science –The Branco Weiss Fellowship, and a Lundeck Research Scholarship. The study authors have reported no relevant financial relationships.

Depression Anxiety. 2013;30:307-314. Abstract


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