White matter abnormalities linked to impulsivity, suicidality in BD
MedWire News: Results from a US study suggest that white matter abnormalities in the left orbital frontal cortex (OFC) are associated with impulsivity and suicidal behavior in patients with bipolar disorder (BD).
"Impulsivity has been demonstrated to be a critical feature of bipolar phenomenology, which is often observed among patients who complete or attempt suicide, and is present even during euthymia," explain Philip Szeszko (The Zucker Hillside Hospital, Glen Oaks, New York) and team.
They add: "Although white matter abnormalities have been implicated in the pathophysiology of BD, their relationship to impulsivity and suicidality in this disorder has not been well-investigated."
The team therefore studied 14 BD patients with a history of suicide attempts, 15 BD patients without such a history, and 15 mentally healthy individuals (controls). There were no significant differences among the three groups regarding age and gender distribution. There were also no significant differences between the two BD groups regarding age at illness onset, and the number of patients with comorbid substance abuse/dependence.
All of the participants underwent diffusion tensor imaging scans of the brain, and those with BD were also assessed using the Barratt Impulsivity Scale, version 11 (BIS-11), the Hamilton Anxiety Rating Scale (HAM-A), the Hamilton Depression Rating Scale (HAM-D), and the Clinician-Administered Rating Scale for Mania (CARS-M).
The team found that BD patients with a history of suicide attempts had significantly lower fractional anisotropy (FA) values for white matter in the left OFC compared with BD patients without such a history. This area of the brain is associated with decision making, impulsivity, and emotion regulation, the researchers note.
There were no significant differences between BD patients without a history of suicide attempts and controls regarding FA values for white matter in this brain region.
The researchers found also that, although there were no significant differences between the two BD groups regarding HAM-A, HAM-D, and CARS-M scores, patients with a history of suicide attempts had significantly higher BIS-11 scores than those without, at 70.7 versus 60.2, indicating increased impulsivity.
In addition, there was a significant negative correlation between mean FA values in the left OFC and motor impulsivity subscale scores on the BIS-11 among BD patients with a history of suicide attempts, but not in those without such a history.
Szeszko and team conclude in Bipolar Disorders: "Our results suggest that impulsivity and suicidal behavior may be related to abnormal left OFC white matter."
They add: "Future studies incorporating both functional and diffusion tensor imaging are needed to more fully examine the functional correlates of abnormal white matter integrity in bipolar disorder patients at increased risk of suicidality."
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By Mark Cowen