Response to electroconvulsive therapy is not consistently replicated across multiple treatment courses.

Electroconvulsive therapy (ECT) is widely used to treat various psychiatric disorders, with patients often undergoing multiple courses of ECT. However, it remains unclear whether responses to one ECT course can be replicated in subsequent treatment courses. A retrospective cohort study at the Institute of Mental Health, Singapore, studied 226 patients who underwent at least two courses of ECT between March 2017 and May 2023. The study compared the correlation of response rates, illness severity, quality of life (QoL), and cognition between 2 courses of ECT using Pearson's chi-square test and Pearson correlation coefficients. The results showed no significant correlation in response rates or cognition between the two courses of ECT. However, small correlations were observed at the group level between the Clinical Global Impression - Improvement (CGI-I) scale, which measures illness severity, and the Quality of Life Enjoyment and Satisfaction Questionnaire - Short Form (Q-LES-Q-SF) scores. Pearson correlation coefficients were r = 0.16 (p = 0.04) for CGI-I and r = 0.28 (p = 0.009) for Q-LES-Q-SF. In subgroup analysis, patients with schizophrenia showed a small correlation between CGI-I (r = 0.21, p = 0.029) and Q-LES-Q SF scores (r = 0.26, p = 0.048), while those with depression showed a moderate correlation in Q-LES-Q SF scores (r = 0.52, p = 0.013), with no correlation in CGI-I. No correlation was observed in the mania or catatonia subgroups. These results suggest that while previous responses to ECT may not reliably predict future outcomes, improvements in illness severity and QoL tend to follow a similar trajectory, highlighting the value of collaborative decision-making in treatment planning.