BACKGROUND: Although major depressive disorder (MDD) and bipolar depression can present with similar symptoms, biological differences exist. One difference is the possible variance in adverse effects associated with treatment. This study examined the association of cognitive impairment and delirium in patients treated with electroconvulsive therapy (ECT) plus lithium for MDD or bipolar depression.

METHODS: The Nationwide Inpatient Sample included 210 adults receiving ECT plus lithium. Descriptive statistics and a Chi-square test were used to evaluate the differences between mild cognitive impairment and drug-induced delirium for those with MDD or bipolar depression. We calculated the odds ratio (OR) for drug-induced delirium in inpatients with MDD (compared to inpatients with bipolar depression) using a binomial logistic regression model.

RESULTS: Mild cognitive impairment was observed in 9.1% of patients with MDD (n = 110), compared to 0 in bipolar depression (n = 100) (P = .002). Drug-induced delirium was more prevalent in MDD (OR 1.19; 95% CI, 1.11 to 1.30).

CONCLUSIONS: ECT plus lithium is associated with less cognitive impairment and drug-induced delirium in bipolar depression compared to MDD. This study may also support biological differences between the 2 types of depression.