Frontothalamic Circuit Abnormalities in Patients With Bipolar Depression and Suicide Attempts

Suicide is the leading cause of premature death among patients with bipolar disorder (BD), so it is imperative to identify biological or psychometric markers for suicide risk. Previous functional neuroimaging studies of the general BD population have focused on abnormalities within cortical-subcortical circuits. The aim of the current study was to examine potential cortico-subcortical circuit abnormalities predictive of suicide attempt in patients with BD.

We examined functional connectivity (FC) based on 5 regions of interest: bilateral anterior cingulate cortex (ACC), medial frontal cortex, inferior frontal cortex, amygdala, and thalamus, by resting-state functional magnetic resonance imaging (rs-fMRI) in 65 participants, including patients with BD and suicide attempts (SA group; n = 24), patients with BD and no suicide attempts (NSA group; n = 15), and healthy control subjects (HC group; n = 26). Patients met DSM-5 criteria for bipolar I disorder with current major depressive episode.

The total patient group (SA+NSA) exhibited significantly lower FC between bilateral thalamus and frontal cortex (F = 35.11, P < .01), and this deficit was most severe in the SA group. In addition, patients demonstrated significantly reduced FC values between bilateral inferior frontal gyrus and both inferior temporal gyrus (F = 20.68, P < .01) and fusiform gyrus (F = 20.98, P < .01), but FC was stronger in the SA group than the NSA group. Both patient groups also exhibited reduced FC based on these seeds including bilateral amygdala, medial frontal cortex, and ACC, but without significant differences between the SA and NSA groups.

The results suggest that reduced FC within specific frontothalamic circuits may increase the vulnerability for suicidal behavior in patients with BD. These FC abnormalities might provide potential predictors of suicide attempt in BD.