© 2019 The Authors. Psychiatry and Clinical Neurosciences published by John Wiley & Sons Australia, Ltd on behalf of Japanese Society of Psychiatry and Neurology Aim: The efficacy of electroconvulsive therapy (ECT) has been established in psychiatric disorders but the high rate of relapse is a critical problem. The current study sought preventative factors associated with relapse after a response to ECT in a continuum of four major psychiatric disorders. Methods: The records of 255 patients with four psychiatric disorders (83 unipolar depression, 60 bipolar depression, 91 schizophrenia, 21 schizoaffective disorder) were retrospectively reviewed. Results: The relapse-free rate of all patients at 1 year was 56.3% in the four psychiatric disorders without a difference. As a result of univariate analysis, three items could be considered as preventative factors associated with relapse: a small number of psychiatric symptom episodes before an acute course of ECT, the use of mood stabilizers, and the use of maintenance ECT. Multivariate analysis was performed, keeping age, sex, and diagnosis constant in addition to the three items, and small number of psychiatric symptom episodes before an acute course of ECT (P = 0.003), the use of lithium (P = 0.025), the use of valproate (P = 0.027), and the use of maintenance ECT (P = 0.001) were found to be significant preventative measures against relapse. Conclusion: The use of mood stabilizers, such as lithium and valproate, and maintenance ECT could be shared preventive factors associated with relapse after a response to ECT in four major psychiatric disorders.