Suicidal ideation is associated with reduced prefrontal activation during a verbal fluency task in patients with major depressive disorder

• We tested prefrontal function vs suicidal ideation in major depressive disorder (MDD).
• Prefrontal function was measured by near-infrared spectroscopy during a fluency task.
• Suicidal ideation was assessed using item 3 of the Hamilton Depression Rating Scale.
• Specific prefrontal cortex regions correlated with the severity of suicidal ideation.
• Near-infrared spectroscopy may be a useful indicator for suicidal ideation in MDD.

BackgroundDespite the known relationship between prefrontal function and increased suicidality during major depressive episodes, the links between prefrontal function and suicidality remain unclear in major depressive disorder (MDD). Suicidal ideation usually precedes a suicide attempt. If prefrontal cortex (PFC) activity is a biomarker for suicidal ideation in depression, monitoring it could be useful for suicide prevention. Therefore, in this study, we assessed the association between prefrontal function and suicidal ideation in MDD.MethodsPrefrontal function in 67 patients with MDD (31 with suicidal ideation and 36 without) and 67 age-, gender-, and intelligence quotient-matched healthy controls (HCs) was evaluated using near-infrared spectroscopy (NIRS) during a verbal fluency task (VFT). Suicidal ideation was assessed using item 3 of the Hamilton Depression Rating Scale (HAMD).ResultsRegional hemodynamic changes were significantly smaller in patients with MDD than in HCs in prefrontal and temporal regions. Hemodynamic changes in the right dorsolateral PFC (DLPFC), orbitofrontal cortex (OFC), and right frontopolar cortex (FPC) regions in patients with MDD with suicidal ideation were significantly smaller than in those without suicidal ideation. In addition, hemodynamic changes correlated negatively with the severity of suicidal ideation in the DLPFC, OFC, and FPC in patients with MDD.LimitationsFurther studies with a larger sample size are required to verify our findings.ConclusionsThese results suggest that the DLPFC, OFC, and FPC are brain substrates of suicidal ideation in depressive states in patients with MDD, and that NIRS data can be employed as a clinically useful biomarker for the assessment of suicide risk.