<p class="first" id="d1872485e196">Pro-inflammatory status has been implicated in
depression and suicidal behaviors.
Polyunsaturated fatty acids (PUFAs) and cytokines, two types of inflammatory biomarkers,
have been associated with suicide, independent of depression severity. How these biomarkers
relate to each other is less clear. We measured plasma phospholipid levels of arachidonic
acid (AA%), docosahexaenoic acid (DHA%), and eicosapentaenoic acid (EPA%) as a percentage
of total phospholipids, as well as serum interleukin-6 (IL-6), interleukin-1β (IL-1β)
and tumor necrosis factor α (TNF-α), in 80 patients with major depressive disorder
(MDD) and 24 healthy controls (HC). Individual PUFA and cytokine species were compared
using ANOVA across four suicide risk-stratified groups: 1) highest-risk, recent (within
5 years) suicide attempters (n = 20); 2) high-risk, severe current suicidal ideators
(having intent or plan) with no recent attempt history (n = 22); 3) low-risk, current
non-ideators who were also lifetime non-attempters (n = 38); and 4) HC (n = 24). None
of the participants were enrolled following an acute suicide attempt. Of biomarkers
studied, only DHA% (p = 0.012) and IL-1β (p = 0.002) differed between groups. In post-hoc
testing, DHA% was lower in attempters than ideators (p = 0.018) or MDD non-ideators
(trend level, p = 0.073). IL-1β was lowest in attempters, differentiating them from
ideators (p = 0.009) and HC (p = 0.004). Recent suicide attempt, one of the most powerful
predictors of suicide risk, was also most closely tied to inflammatory indices in
this study. Low DHA% as an indicator of suicide risk is consistent with previous reports;
however, lower IL-1β was unexpected and may relate to acuity/chronicity of inflammation.
There is a need for prospective studies of immune status with respect to suicidal
behaviors.
</p>