Resting State MRI Amplitude of Low Frequency Fluctuations Associated With Suicidal Ideation in Bipolar Depression.

Objective: Suicidal ideation (SI) is a risk factor for completed suicide. Our previous resting state functional magnetic resonance imaging (fMRI) study found that higher amplitude of low frequency fluctuation (ALFF) in right hippocampus and thalamus was associated with SI in major depressive disorder (MDD). The present study aimed to evaluate that association in participants with bipolar disorder (BD). Methods: Thirty depressed, adult participants with a DSM-IV diagnosis of BD had resting state fMRI scans. Region-of-interest (ROI) analyses used ALFF values within areas that were previously associated with SI in MDD. Spearman rank correlation and ordinal regression analyses were performed to assess associations between ALFF values and the SI item of the Montgomery-Asberg Depression Rating Scale. Exploratory whole-brain analyses identified regions where ALFF was associated with SI. Results: Within the right hippocampus region, SI was positively associated with ALFF (Spearman R = 0.490, P = .0060). Ordinal regression analysis indicated that for every 0.1-unit increase in ALFF in that region, the odds of having higher SI were increased by 35% (odds ratio = 1.35; 95% confidence interval, 1.08-1.73; P = .012). Within the previously identified thalamus cluster, SI was associated with ALFF only at a trend level (Spearman R = 0.310, P = .069). Whole-brain analyses identified 3 clusters of positive association between SI and ALFF, 1 of which was located in the right hippocampus. Conclusions: This study found that our previous finding of positive association between SI and ALFF in the right hippocampus extended to bipolar depression. Future studies should examine the clinical utility of this association, and the role of the hippocampus in SI. Trial Registration: Data used for this secondary analysis came from studies with ClinicalTrials.gov identifiers NCT02239094 (January 2015 through September 2016) and NCT02473250 (January 2015 through December 2019).