Mood disorders and incident ICU delirium: Distinct risk profiles across clinical subgroups and diagnostic subtypes

Mood disorders are hypothesized to increase susceptibility to intensive care unit (ICU) delirium, but the evidence remains limited. This study evaluated the overall association and investigated risk heterogeneity across clinical subgroups and diagnostic subtypes.

Using the Medical Information Mart for Intensive Care (MIMIC)-IV database, we identified incident delirium via the Confusion Assessment Method for the ICU (CAM-ICU). Primary analysis employed 1:3 propensity score matching to estimate the overall association and explore risk variation across clinical subgroups. Secondary analysis used multivariable Cox regression on the full cohort to investigate risk heterogeneity across diagnostic subtypes.

In 36,944 matched patients, mood disorders were independently associated with an increased risk of delirium (HR, 1.24; 95% CI, 1.19-1.30). Subgroup analyses within this cohort showed higher relative risk in patients typically considered low-risk: those younger than 65 years, without sepsis, and not receiving advanced critical care interventions. Notably, subtype analysis in the full cohort revealed a distinct risk gradient: bipolar disorder conferred the highest risk (HR, 1.54; 95% CI, 1.40-1.69), followed by major depressive disorder (HR, 1.39; 95% CI, 1.32-1.47), while other mood disorders showed no significant association (HR, 1.04; 95% CI, 0.97-1.11).

Mood disorders are independent risk factors for ICU delirium, particularly robust in younger or lower-acuity populations. This risk is primarily driven by bipolar disorder and major depressive disorder. Consequently, incorporating mood disorder history may serve as an additional marker of vulnerability to inform future delirium risk stratification for patients with major affective disorders, even without traditional high-risk characteristics.