Neural Correlates of Suicidal Ideation and Its Reduction in Depression

Suicidal ideation in treatment-resistant major depression is linked to activity in the infralimbic cortex (Brodmann area 25). In 19 medication-free patients, higher baseline metabolism in this brain region correlated with more severe suicidal thoughts, but not with overall mood. A single ketamine infusion (0.5 mg/kg) reduced both suicidal ideation and metabolism in the infralimbic cortex, and the degree of metabolic decrease matched the degree of symptom improvement. Other brain areas examined—the amygdala and subgenual anterior cingulate cortex—showed no significant association with suicidal ideation or depression. The infralimbic cortex may be a specific neural substrate for suicidal thinking, distinct from general mood.

Study at a glance

Abstract

BACKGROUND: The neural correlates of suicidal ideation and its reduction after treatment are unknown. We hypothesized that increased regional cerebral glucose metabolism in the infralimbic cortex (Brodmann area 25), amygdala, and subgenual anterior cingulate cortex would be associated with suicidal ideation and its reduction after ketamine infusion. METHODS: Medication-free patients (n=19) with treatment-resistant major depressive disorder underwent positron emission tomography imaging at baseline and 230 minutes after an open-label ketamine infusion (0.5 mg/kg for 40 minutes). RESULTS: Baseline suicidal ideation and regional cerebral glucose metabolism in the infralimbic cortex were significantly correlated (r=.59, P=.007); but not overall mood scores (r=-.07, P=.79). Reductions in suicidal ideation after ketamine infusion were correlated with decreased regional cerebral glucose metabolism in the infralimbic cortex (r=.54, P=.02). Metabolism in other areas of interest was not significantly correlated with suicidal ideation or depression. CONCLUSION: The infralimbic cortex may be implicated in suicidal ideation.