Abstract
Previous neuroimaging studies have revealed frontal and temporal functional abnormalities in patients with major depressive disorder (MDD) and a history of suicidal behavior. However, it is unknown whether multi-channel near-infrared spectroscopy (NIRS) signal changes among individuals with MDD are associated with a history of suicide attempts and a diathesis for suicidal behavior (impulsivity, hopelessness, and aggression). Therefore, we aimed to explore frontotemporal hemodynamic responses in depressed patients with a history of suicide attempts using 52-channel NIRS. We recruited 30 patients with MDD and a history of suicidal behavior (suicide attempters; SAs), 38 patient controls without suicidal behavior (non-attempters; NAs), and 40 healthy controls (HCs) matched by age, gender ratio, and estimated IQ. Regional hemodynamic responses during a verbal fluency task (VFT) were monitored using NIRS. Our results showed that severities of depression, impulsivity, aggression, and hopelessness were similar between SAs and NAs. Both patient groups had significantly reduced activation compared with HCs in the bilateral frontotemporal regions. Post hoc analyses revealed that SAs exhibited a smaller hemodynamic response in the left precentral gyrus than NAs and HCs. Furthermore, the reduced response in the left inferior frontal gyrus was negatively correlated with impulsivity level and hemodynamic responses in the right middle frontal gyrus were negatively associated with hopelessness and aggression in SAs but not in NAs and HCs. Our findings suggest that MDD patients with a history of suicide attempts demonstrate patterns of VFT-induced NIRS signal changes different from those demonstrated by individuals without a history of suicidal behaviors, even in cases where clinical symptoms are similar. NIRS has a relatively high time resolution, which may help visually differentiate SAs from NAs.
Highlights
Every year, one million individuals world over die from suicide [1]
For the analysis of near-infrared spectroscopy (NIRS) data, we focused on oxygenated hemoglobin (oxy-Hb) because it is thought that cortical activation is more directly reflected by a task-related change in this parameter than by a change in deoxy-Hb, as indicated by a stronger correlation with blood oxygenation level-dependent signals measured on functional MRI (fMRI) [41]
Both major depressive disorder (MDD) patient groups scored higher than healthy controls (HCs) on impulsivity, aggression, and hopelessness, whereas no significant differences were observed between the suicide attempters (SAs) and NA
Summary
One million individuals world over die from suicide [1]. This is a serious global health problem, but suicide is difficult to predict and prevent in majority of the people at risk. A recent MRI study indicated that suicide attempters (SAs) with a past history of mood disorders have reduced activity in the left ventrolateral prefrontal cortices compared with healthy controls (HCs) and with patient controls with a past history of mood disorders but not of suicidal behavior [8]. One recent investigation found that compared with depressed individuals with only suicidal thoughts, depressed individuals without suicide thoughts and plans, and healthy controls, depressed individuals with suicide plans showed relative hypometabolism in the right middle frontal gyrus and right inferior parietal lobe [15] These neuroimaging studies have revealed altered brain structure and regional activity associated with vulnerability for suicide risk in psychiatric disorders [16, 17]
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