Bipolar Disorder Hospitalizations and Substance Use Disorders: A Nationwide Retrospective Study From 2008 To 2015

Bipolar Disorder (BD) is often complicated by co-occurring substance use disorders (SUD). We assessed the prevalence of SUD among BD hospitalization episodes and analyzed its association with hospitalization outcomes.

We performed a retrospective observational study using a database containing all hospitalizations registered in Portuguese public hospitals from 2008 to 2015. Hospitalizations with a primary or secondary diagnosis of BD were selected. To compare episodes with and without a diagnosis of SUD, an independent sample t-test was used for age, whereas the non-parametric Mann-Whitney U test was used for LoS, CCI, and charges. Sex, in-hospital mortality, re-hospitalizations, and psychiatric comorbidities were analyzed using the Pearson's chi-squared test.

SUD was registered in 11.3% of episodes, with alcohol use disorder being the most prevalent (5.8%). A non-linear increase in the number of hospitalizations throughout the study period was found. Episodes with a concomitant register of SUD were associated with younger (44.1 ± 12.5 years old) and male hospitalizations (56.6%), shorter length of stay (LoS) (15.0 (8.0;24.0) days), higher Charlson Comorbidity Index (CCI) (0.24 ± 0.76), and with higher rates of attention-deficit, conduct, and disruptive behavior disorders, personality disorders, and suicide and intentional self-inflicted injury, compared to those without this comorbidity.

Comorbid SUD increased and had a measurable impact on BD hospitalization outcomes. Timely detection and management of SUD among BD patients may likely prevent the high burden.