To Örebro University

During the first year following electroconvulsive therapy (ECT) for major depressive disorder (MDD) there is a large risk of relapse. Previous studies have shown favourable results for lithium after ECT for MDD. However, lithium is infrequently prescribed after ECT. While some evidence exists for other pharmacological strategies such as TCAs and TCA-lithium combinations, comparative data remain limited. The aim of this study was to explore pharmacological treatments after ECT for MDD and analyse their association with relapse following response to ECT for MDD. We hypothesized that lithium would be associated with a lower risk of relapse. We conducted a nationwide cohort study using data from Swedish registers. Patients 18 years or older with MDD who received ECT 2013-2019 and responded distinctly to ECT were followed for a year. Specified drugs dispensed up to four weeks after the ECT series were considered the exposure. Relapse was defined as psychiatric hospitalisation, renewed ECT, intentional self-harm, or death by suicide. Adjusted hazard ratios (aHR) and 95% confidence intervals (CI) were estimated using Cox models controlled for several potential confounders. The study population included 2 858 patients with distinct response to ECT. The most common psychiatric drugs dispensed after ECT were antipsychotics (39.7%), mirtazapine (38.0%), and selective serotonin reuptake inhibitors (SSRI) (35.9%). There was a statistically non-significant lower risk of relapse associated with lithium (aHR 0.86, 95% CI 0.69-1.07, p = 0.17). Antipsychotics were associated with a greater risk of relapse (aHR 1.17, 95% CI 1.05-1.31, p = 0.006). For other pharmacological treatments there were no associations with risk of relapse.