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Table 2: Most relevant DTI studies about alterations in WM integrity and suicidal behavior
Authors Study Sample Main results Limitations Conclusion
design
Olvet et al. [15] Cross‑ 13 suicide Suicide attempters reported The small sample size did not WM abnormalities
sectional attempters lower FA relative to MDD allow the generalization of findings. may contribute to
with MDD, 39 non‑attempters and HP in the HP group was younger than the functional deficits
non‑attempters DLPFC. A significant cluster non‑attempter group. The most associated with
with MDD, and within the right DLPFC has recent suicide attempt ranged suicidal behavior
46 HP been confirmed according to from 19 days to 39 years before
uncorrected TBSS findings. the DTI scan. The possible effect
No differences in ADC when of medications (antidepressants)
comparing the three groups should be not excluded. Finally, the
using ROI or TBSS methods cross‑sectional nature of this study
were found should be considered a further
additional limitation
Lopez‑ Cross‑ 40 veterans with Left and right thalamic The small sample size did not allow Thalamic
Larson sectional mild TBI and no volumes were reported as the generalization of findings. Of enlargement and
et al. [16] SB, 19 veterans significantly increased in note, the study included only male increased FA in
with mild TBI those with TBI and a history subjects. The cross‑sectional nature subjects with TBI
and a history of of SB compared to the HP, of this study should be considered a and a history of
SB, and 15 HP TBI and a history of SB, and further additional limitation SB suggested that
the combined group. Veterans this region may
with TBI and a history of SB be considered a
had increased FA bilaterally potential biomarker of
compared to the HP, HP and suicidal behavior
TBI with a history of SB group,
and the TBI with a history of
SB only group. Significant
positive associations were
found for bilateral ATR and
BIS in those with TBI and a
history of SB
Yurgelun‑ Cross‑ Fifteen male A significant reduction in FA The small sample size did not allow A potential
Todd et al. [17] sectional veterans with values of the left cingulum and the generalization of findings. The neurobiological
TBI and 17 left/total genu was observed cross‑sectional nature of this study vulnerability to
matched HP in the TBI group compared to should be considered a further suicidal risk may
HP. Subjects with TBI were additional limitation be mediated by the
more likely to have higher significant reduction
impulsivity than HP. A positive in FA of frontal WM
correlation between current tracts in veterans with
suicidal ideation, impulsivity, mild TBI associated
and total and right cingulum with both impulsivity
FA has been observed and suicidality
Jia et al. [123] Cross‑ 63 patients with Both groups of depressed The study may be limited in terms of WM alterations of
sectional MDD (23 with patients had reduced fiber power to examine variability in brain frontothalamic circuits
and 40 without a projections through the anatomy concerning any specific may contribute to
history of suicide ALIC to the left medial method of suicide attempts, specific cognitive/affective
attempts) and frontal cortex, orbitofrontal previous treatments, or number of deficits increasing
46 HP cortex, and thalamus. Those previous attempts and depressive vulnerability for
with a history of suicide episodes. Personality has not suicidal behavior in
attempts were more likely been evaluated. According to DTI depressed patients
to have alterations in the analyses, the ability of the present
left orbitofrontal cortex and study to distinguish the directionality
thalamus than those without a of altered fiber tracts is very
history of suicide attempts limited. Furthermore, the degree to
which alterations in the ALIC are
restricted to the left hemisphere
needs to be evaluated. Finally, the
present findings may be not able to
establish the direction of causality
ADC: apparent diffusion coefficient; ALIC: left anterior limb of the internal capsule; ATR: anterior thalamic radiations; BD: bipolar disorder; BIS: Barratt Impulsiveness
Scale; DTI: diffusion tensor imaging; DLPFC: dorsomedial prefrontal cortex; FA: fractional anisotropy; HP: healthy participants; MDD: major depressive disorder;
ROI: region of interest; SB: suicidal behavior; TBI: traumatic brain injury; TBSS: tract‑based spatial statistics; WM: white matter

Some limitations potentially contributing to the possible confounding variables (such as vascular
lack of consistency of the present findings need to risk factors) together with history of substance abuse/
be addressed. First, WMHs in patients with MDD dependence and prior mood episodesas as well as
should be interpreted as an extreme consequence of the burden of comorbidities. Another important
underlying microstructural dysfunctions affecting caveat regards the use of psychotropic medications
brain connectivity. Second, most studies did not potentially influencing both the presence and severity
assess patients for the presence and severity of of WM lesions.

210 Neuroimmunol Neuroinflammation | Volume 2 | Issue 4 | October 15, 2015