Cingulum Bundle White Matter in Bipolar Disorder: Relationship With Impulsivity and Suicide Attempt

Area of Science:

• Neuroscience
• Psychiatry
• Neuroimaging

Background:

• Bipolar disorder (BD) is associated with high suicide rates.
• Fronto-limbic brain network alterations are implicated in BD and suicide.
• Neurobiological underpinnings of suicide in BD require further investigation.

Purpose of the Study:

• To examine fronto-limbic white matter microstructure in individuals with bipolar disorder (BD).
• To investigate the association between white matter integrity and suicide attempts in BD.
• To replicate findings in independent US and UK cohorts.

Main Methods:

• Diffusion tensor imaging (DTI) was used to assess fractional anisotropy (FA) in specific white matter tracts.
• Two independent samples were analyzed: US military veterans and the UK Biobank.
• FA values were correlated with the UPPS-P Impulsive Behavior Scale.

Main Results:

• Lower FA in the cingulum hippocampus (CGH) was found in individuals with BD and a history of suicide attempts (BD/SA+) compared to those without (BD/SA-) in both samples.
• Reduced CGH FA in the US sample was associated with higher negative urgency, a facet of impulsivity.
• No significant differences in FA were observed in the cingulum cingulate (CGC) or uncinate fasciculus (UF).

Conclusions:

• Consistent evidence from two independent samples suggests reduced white matter integrity in the CGH is linked to suicide attempts in BD.
• Negative urgency may mediate the relationship between cingulum white matter integrity and suicide risk in BD.