OBJECTIVESThe aims of the present study were to describe the short-term rate of subjective memory worsening (SMW) and identify factors of importance for SMW in a large clinical sample treated for depression with electroconvulsive therapy (ECT). METHODSThis register-based study included 1212 patients from the Swedish National Quality Register for ECT. Subjective memory worsening was defined as a 2-point worsening on the memory item of the Comprehensive Psychopathological Rating Scale from before to within 1 week after treatment. Associations between patient characteristics and treatment factors were examined using logistic regression. RESULTSSubjective memory worsening was experienced in 26%. It was more common in women than in men (31% vs 18%; P < 0.001) and more common in patients aged 18 to 39 years than in patients 65 years or older (32% vs 22%; P = 0.008). Patients with less subjective memory disturbances before ECT had a greater risk of SMW. Patients in remission after ECT had a lower risk of SMW. A brief pulse width stimulus gave higher risk of SMW compared with ultrabrief pulse (odds ratio, 1.61; 95% confidence interval, 1.05–2.47). CONCLUSIONSSubjective memory worsening is reported by a minority of patients. However, young women are at risk of experiencing SMW. Ultrabrief pulse width stimulus could be considered for patients treated with unilateral electrode placement who experience SMW. Each patient should be monitored with regard to symptoms and adverse effects, and treatment should be adjusted on an individual basis to maximize the clinical effect and with efforts to minimize the cognitive adverse effects.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.