Mixed state and suicide: Is the effect of mixed state on suicidal behavior more than the sum of its parts?

Abstract

Objective: To assess whether suicidal behavior during mixed states exceeds that expected from the manic or depressive components alone. Methods: This study included 429 participants with bipolar disorder from the National Institute of Mental Health Collaborative Depression Study (CDS). Mood and suicidal behavior were captured using the Longitudinal Interval Follow-up Evaluation and the Schedule of Affective Disorders and Schizophrenia. Suicidal behavior during each mood state, relative to euthymia, was analyzed using Cox regression to allow for repeated events, with a frailty term to account for intra-participant correlation. Mixed states were modeled as a depression-by-mania interaction. Results: Individuals with a history of mixed states were at higher risk of suicidal behavior and spent more time depressed, compared to subjects with no such history. In bipolar I disorder, risk increased during episodes of mania (hazard ratio [HR]: 1.96, 95% confidence interval [CI]: 1.28-2.99, P =.0019) and depression (HR: 5.49, 95% CI: 4.01-7.51, P