Major depressive disorder is not only the most widespread mental disorder in the world, it is a disorder on the rise. In cases of particularly severe forms of depression, when all other treatment options have failed, the use of electroconvulsive therapy (ECT) is a recommended treatment option for patients. ECT has been in use in psychiatric practice for over 70 years and is now undergoing something of a restricted renaissance following a sharp decline in its use in the 1970s. Despite its success in treating severe depression there is continued debate as to the effectiveness of ECT: in some studies, it is argued that ECT is marginally more effective than sham ECT. In addition, there is still no clear explanation of how ECT works; among the range of hypotheses proposed it is claimed that ECT may work by harnessing placebo effects. In light of the uncertainties over the mechanism of action of ECT and given the risk of serious side effects that ECT may produce, I contend that the process of informed consent must include comprehensive accounts of these uncertainties. I examine the possible consequences of providing adequate information to potential ECT patients, including the consideration that ECT may still prove to be effective even if physicians are open about the possibility of it working as a placebo. I conclude that if we value patient autonomy as well as the professional reputation of medical practitioners, a fuller description of ECT must be provided to patients and their carers.