Neural Correlates of Suicidal Ideation and Its Reduction in Depression

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.