Co-occurrence of bipolar disorder and personality disorders in the United States: Prevalence, suicidality, and the impact of substance abuse

Background: This study investigates prevalence rates of specific personality disorders (PDs) in individuals with bipolar disorder (BD) and their impact on substance abuse and suicidality, addressing existing gaps in the literature.Methods: Using Nationwide Inpatient Sample data (2016-2020), adult hospitalizations for BD with coexisting PDs were analyzed. Study variables were defined using ICD-10-CM codes. Prevalence of PD were reported as cases per 100,000 BD admissions. Regression models assessed the association between substance abuse and suicidality.Results: About 993,000 admissions for BD were analyzed. The cohort was predominantly Caucasian (70.5 %) with higher female representation (54.5 %). The mean age was 41 years. 89.4 % of individuals had a Charlson Co-morbidity Index score <= 1. The most common diagnostic subtype was manic episode of BD with or without psychotic features (32.3 %). Coexisting PDs were observed in 12.2 % of the population, with borderline PD (8.2 %) and antisocial PD (2.6 %) being most prevalent. Substance abuse was common (44.8 %), with cannabis (23.8 %), alcohol (19.4 %), cocaine (10.5 %), and opioids (9.6 %) being most reported. Substance abuse was higher in individuals with BD and PD (50 %) compared to BD alone (44.1 %). 596 suicide attempts were recorded (60 per 100,000 BD admissions). Substance abuse and coexisting PD in bipolar individuals elevated the likelihood of attempts (P < 0.001). Limitations: Use of administrative data (retrospective, inpatient); treatment not studied.Conclusion: The study reveals a notable prevalence of PDs in individuals with BD, with increased likelihood of substance abuse and suicide attempts in those with coexisting BD and PD compared to BD alone.