Electroconvulsive therapy (ECT) is one of the most effective treatments available for severe depression, with a response rate of about 73% and a remission rate of 51% in moderate to severe cases. For context, “response” means a substantial reduction in symptoms, while “remission” means symptoms are largely gone. These numbers come from a large analysis of Scottish national data spanning a decade, and they hold up even though many patients receiving ECT have already failed other treatments.
Response Rates by Condition
ECT’s effectiveness varies depending on what it’s treating. In major depression, the 73% response rate is already strong, but certain subgroups do even better. Older adults, people with psychotic depression (depression with delusions or hallucinations), and those with severe melancholic features tend to respond particularly well. A high severity of suicidal behavior also predicts a stronger response, likely because the most acute presentations of depression are the ones ECT is best suited to treat.
For treatment-resistant depression, defined as failing at least two different classes of antidepressants, ECT still works remarkably well. One study found a response rate of 85.7%, with about 55% of those patients reaching full remission. That’s notable because these are patients whose depression didn’t budge with standard medications. If patients relapse and need a second round of ECT, the response rate drops somewhat to around 67%, which is still significant.
Catatonia, a condition involving severe disruptions in movement and responsiveness, is where ECT performs best of all. Response rates reach 80 to 100%, making it essentially the gold-standard treatment. In one study, 19 out of 20 patients with catatonia responded to ECT.
How Quickly It Works
A typical course of ECT for depression involves 6 to 12 sessions, usually given two or three times per week. In about two-thirds of studies, the average number of sessions falls between 6 and 10. Treatment continues until symptoms resolve or until improvement plateaus for two consecutive sessions, at which point additional sessions are unlikely to add benefit. This means most people can expect a treatment course lasting roughly 2 to 6 weeks, which is considerably faster than waiting 4 to 8 weeks for an antidepressant to take full effect.
How ECT Compares to Other Options
A network meta-analysis comparing ECT, IV ketamine, and repetitive transcranial magnetic stimulation (TMS) for treatment-resistant depression found no significant differences in response or remission rates among the three. All three were clearly superior to control conditions. The practical differences lie elsewhere: ketamine had higher “acceptability,” meaning fewer patients dropped out, while ECT requires anesthesia and a clinical setting. TMS is noninvasive but typically requires daily sessions over several weeks. For the most severe presentations, ECT remains the default choice because it has the longest track record and the most robust evidence base across a wider range of conditions.
The Relapse Problem
ECT’s biggest limitation isn’t getting people better. It’s keeping them better. Roughly 50% of patients who respond well to ECT relapse within 12 months, with most relapses happening in the first 6 months. This is a well-recognized challenge, and relapse prevention is now a major focus of post-ECT care.
The standard approach is continuation therapy after the acute course ends. This typically means staying on antidepressant medication, but for patients at high risk of relapse (particularly those with severe or psychotic depression), continuation ECT is also recommended. Rather than stopping ECT abruptly, sessions are gradually tapered over weeks or months. For patients who relapse despite medication, maintenance ECT on an ongoing schedule, combined with pharmacotherapy, is an option supported by randomized trials.
Memory and Cognitive Side Effects
Memory problems are the most common concern patients have about ECT, and the concern is legitimate. About 60% of patients report some degree of memory difficulty, with 40% saying these problems lasted from several weeks to several years.
There are two distinct types of memory effects. The first is trouble forming new memories in the days immediately after treatment. This clears up relatively quickly. Meta-analyses show that new learning ability is impaired right after ECT but returns to baseline within about 14 days. Beyond two weeks, objective testing shows no ongoing impairment in forming new memories.
The second type is retrograde amnesia: losing memories from before or during the treatment period. This is more concerning because it can persist. Objective testing shows that some autobiographical memory loss exceeds the normal fading of memories over time, and in studies tracking patients for at least a year, this loss did not fully resolve. Some memories from the weeks or months surrounding treatment may simply not come back. The degree of loss depends heavily on how ECT is delivered.
How Electrode Placement Affects Side Effects
Modern ECT uses two main electrode placements: right unilateral (one side of the head) and bilateral (both sides). When energy dosing is properly calibrated, both approaches produce equivalent antidepressant results. The difference shows up in side effects. Patients receiving right unilateral ECT experience less post-treatment confusion, better preservation of general cognitive function and verbal memory, and less autobiographical memory loss. Bilateral ECT produces more marked memory effects that persist for at least three months. For this reason, right unilateral placement at an adequate energy dose has become the preferred starting approach at most treatment centers.
What Happens in the Brain
ECT’s exact mechanism isn’t fully understood, but the leading theory centers on neuroplasticity: the brain’s ability to grow and reorganize neural connections. Animal studies show that electrical stimulation triggers the growth of new neurons in the hippocampus, a brain region critical for mood regulation and memory. ECT also appears to increase levels of a protein that supports neuron survival and the formation of new connections, though human studies measuring this protein in blood samples have shown mixed results. The takeaway is that ECT likely works not by “shocking” the brain into functioning, but by stimulating biological repair processes that depression disrupts.
Who Benefits Most
Not everyone responds equally to ECT. The clinical features most strongly associated with a good outcome include older age, psychotic depression, melancholic depression (characterized by profound loss of pleasure, worse mood in the morning, significant weight loss, and excessive guilt), and high severity of the current episode. Speed of initial response also matters: patients who start improving in the first few sessions tend to have better overall outcomes. Younger patients with chronic, milder depression and multiple failed medication trials sometimes respond less robustly, though ECT can still be effective for this group when other options have been exhausted.