Impulsivity and Psychiatric Diagnoses as Mediators of Suicidal Ideation and Suicide Attempts Among Veterans With Traumatic Brain Injury.

OBJECTIVE: Traumatic brain injury (TBI) is a risk factor for suicide, but questions related to mechanisms remain unanswered. Impulsivity is a risk factor for suicide and is a common sequela of TBI. The authors explored the relationships between TBI and both suicidal ideation and suicide attempts and explored whether impulsivity and comorbid psychiatric diagnoses mediate these relationships. METHODS: This cross-sectional retrospective chart review study included 164 veterans enrolled in a previous study. Sixty-nine veterans had no TBI history, and 95 had a TBI history (mild, N=44; moderate, N=13; severe, N=12; and unclear severity, N=26). To examine the associations between TBI and suicidal ideation or suicide attempts, as well as potential mediators of these relationships, chi-square tests, t tests, and logistic regression models were used. RESULTS: Unadjusted analyses indicated that veterans with TBI were more likely to report suicidal ideation; however, in analyses controlling for mediators, this relationship was no longer significant. Among veterans with TBI, suicidal ideation was related most strongly to high impulsivity (odds ratio=15.35, 95% CI=2.43-96.79), followed by depression (odds ratio=5.73, 95% CI=2.53-12.99) and posttraumatic stress disorder (odds ratio=2.57, 95% CI=1.03-6.42). TBI was not related to suicide attempts, yet suicide attempts were related to high impulsivity (odds ratio=6.95, 95% CI=1.24-38.75) and depression (odds ratio=3.89, 95% CI=1.56-9.40). CONCLUSIONS: These findings suggest that impulsivity, followed by psychiatric diagnoses, most strongly mediate the relationships between TBI and both suicidal ideation and suicide attempts. Impulsivity may be mechanistically related to, and serve as a future treatment target for, suicidality among veterans with TBI.

Reduced lateral prefrontal cortical volume is associated with performance on the modified Iowa Gambling Task: A surface based morphometric analysis of previously deployed veterans.

Post-traumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI) are two of the most common consequences of combat deployment. Estimates of comorbidity of PTSD and mTBI are as high as 42% in combat exposed Operation Enduring Freedom, Operation Iraqi Freedom and Operation New Dawn (OEF/OIF/OND) Veterans. Combat deployed Veterans with PTSD and/or mTBI exhibit deficits in classic executive function (EF) tasks. Similarly, the extant neuroimaging literature consistently indicates abnormalities of the ventromedial prefrontal cortex (vmPFC) and amygdala/hippocampal complex in these individuals. While studies examining deficits in classical EF constructs and aberrant neural circuitry have been widely replicated, it is surprising that little research examining reward processing and decision-making has been conducted in these individuals, specifically, because the vmPFC has long been implicated in underlying such processes. Therefore, the current study employed the modified Iowa Gambling Task (mIGT) and structural neuroimaging to assess whether behavioral measures related to reward processing and decision-making were compromised and related to cortical morphometric features of OEF/OIF/OND Veterans with PTSD, mTBI, or co-occurring PTSD/mTBI. Results indicated that gray matter morphometry in the lateral prefrontal cortex (lPFC) predicted performance on the mIGT among all three groups and was significantly reduced, as compared to the control group.

HJURP is a CENP-A chromatin assembly factor sufficient to form a functional de novo kinetochore.

Centromeres of higher eukaryotes are epigenetically marked by the centromere-specific CENP-A nucleosome. New CENP-A recruitment requires the CENP-A histone chaperone HJURP. In this paper, we show that a LacI (Lac repressor) fusion of HJURP drove the stable recruitment of CENP-A to a LacO (Lac operon) array at a noncentromeric locus. Ectopically targeted CENP-A chromatin at the LacO array was sufficient to direct the assembly of a functional centromere as indicated by the recruitment of the constitutive centromere-associated network proteins, the microtubule-binding protein NDC80, and the formation of stable kinetochore-microtubule attachments. An amino-terminal fragment of HJURP was able to assemble CENP-A nucleosomes in vitro, demonstrating that HJURP is a chromatin assembly factor. Furthermore, HJURP recruitment to endogenous centromeres required the Mis18 complex. Together, these data suggest that the role of the Mis18 complex in CENP-A deposition is to recruit HJURP and that the CENP-A nucleosome assembly activity of HJURP is responsible for centromeric chromatin assembly to maintain the epigenetic mark.