Design: National, register-based randomized trial, unmasked with two treatment arms. Primary objective: To test the hypothesis that a 1.0 ms pulse width stimulus produces a higher remission rate (\< 11 on the MADRS-S) than a 0.5ms pulse width stimulus. Secondary objectives include testing for differences in: self-rated global health measured with the EQ5D-VAS subjective memory worsening (increase of 2 on the memory item of the CPRS) antidepressive response (decrease of 50% on the MADRS-S) number of ECTs in the treatment series readmission and suicide rate within 6 months Study population: patients with unipolar or bipolar depression. Sample size: 800 patients, 400 patients in each arm. Inclusion criteria: At least 18 years of age at the time of inclusion Diagnostic criteria fulfilled for unipolar, or bipolar depressive episode according to ICD-10. An indication for and accepting ECT A Swedish personal identity number. Capable of giving informed consent. Exclusion criteria: If the investigator judges a certain pulse width to be inappropriate for the patient. Inclusion time 2019-05-01-2022-11-15. Abbreviations 1. CGI: Clinical Global Impression Scale 2. CPRS: The Comprehensive Psychopathological Rating Scale 3. ECT: Electroconvulsive therapy 4. EQ5D: EuroQual-group 5 Dimensions Scale 5. ICD-10: International Statistical Classification of Diseases and Related Health Problems. - 10th revision, 6. MADRS-S: Montgomery-Åsberg Depression Rating Scale, self assessed version. 7. Q-ECT: Swedish national quality register for ECT 8. VAS: Visual analogue scale