Electroconvulsive therapy (ECT) works by delivering a brief, controlled electrical current to the brain under general anesthesia, triggering a short seizure that sets off a cascade of biological changes. These changes include growth of new brain cells, strengthened connections between brain regions, and shifts in brain chemistry. With a response rate of about 73% and a remission rate of 51% for moderate to severe depression, ECT remains one of the most effective treatments available, particularly when medications have failed.
What Happens During a Session
ECT is done under general anesthesia, so you’re completely unconscious and feel nothing during the procedure. After the anesthetic takes effect, a muscle relaxant is given to prevent your body from tensing or moving during the seizure. A bite guard is placed in your mouth, and electrodes are positioned on your scalp.
A precisely calibrated electrical current is then delivered for a few seconds. This triggers a seizure in the brain that typically lasts 30 to 60 seconds. Because of the muscle relaxant, the only visible sign might be a slight movement of the toes or fingers. The entire procedure, from entering the treatment room to waking up in recovery, takes roughly 30 to 45 minutes. Most people are alert enough to go home within an hour or two.
How ECT Changes the Brain
The therapeutic seizure isn’t random electrical chaos. It kicks off specific biological processes that appear to reverse some of the damage depression inflicts on the brain.
One of the most well-documented effects involves a protein called BDNF (brain-derived neurotrophic factor), which acts like fertilizer for brain cells. Depression is associated with low BDNF levels, and ECT reliably raises them. A meta-analysis confirmed an overall increase in blood BDNF levels after a course of ECT, and the size of that increase correlates with how much symptoms improve. In people who respond well to ECT, BDNF rises significantly. In non-responders, levels tend to stay flat.
ECT also drives measurable structural changes. Brain imaging studies show that the hippocampus, a region critical for mood regulation and memory that tends to shrink in people with chronic depression, actually grows in volume after ECT. Specific subregions of the right hippocampus increase in size among responders. More importantly, the connections between the hippocampus and other brain areas strengthen and normalize. One study found a direct correlation between increased right hippocampal connectivity and reduction in depressive symptoms: the more connectivity improved, the better people felt.
Beyond BDNF and structural growth, ECT affects multiple signaling systems in the brain, including neurotransmitters and neuropeptides. The exact mix of chemical changes is still being mapped, but the overall picture is clear: ECT doesn’t just mask symptoms the way some treatments might. It promotes physical repair and regrowth in brain regions that depression has compromised.
A Typical Course of Treatment
A standard course of ECT for depression involves 6 to 12 sessions. In the U.S., sessions are typically scheduled three times per week, while in the U.K., twice-weekly is more common. In about two-thirds of studies, patients receive between 6 and 10 total treatments. Three-times-weekly schedules produce faster improvement but may carry slightly higher cognitive side effects, so clinicians sometimes start frequent and taper down as symptoms lift.
If there’s no improvement at all after six sessions, the treatment is generally reconsidered. If there’s partial improvement, continuing up to 12 sessions is reasonable, since a substantial number of partial responders go on to achieve full remission with additional treatments.
Electrode Placement Matters
There are two main ways to position the electrodes: on one side of the head (right unilateral) or on both sides (bilateral). This choice significantly affects both effectiveness and side effects.
Right unilateral placement causes less memory disruption and less post-treatment confusion. For many patients, particularly those with reactive depression triggered by life events, it works just as well as bilateral placement, though improvement may come a bit more slowly. Bilateral placement tends to work faster and may be more effective for severe, biologically driven depression, making it the better choice when someone is in immediate danger or declining rapidly.
Ultrashort Pulse Technology
The electrical pulse itself has evolved. Traditional ECT uses a “brief pulse” of electricity, but newer machines can deliver an “ultrabrief pulse,” which is a fraction of the duration. When combined with right unilateral placement, ultrabrief pulse ECT substantially reduces cognitive side effects, including faster recovery of orientation after each session, less retrograde amnesia, and better retention of newly learned information. The tradeoff is that it may require more sessions to achieve the same level of improvement. For patients where minimizing memory effects is the top priority, ultrabrief pulse is the preferred approach. When speed is critical, such as for someone at serious risk of suicide, standard brief pulse remains the go-to.
Memory and Cognitive Side Effects
Memory disruption is the most significant side effect and the one that concerns people most. ECT can cause two types of memory problems. Anterograde amnesia is difficulty forming new memories during the treatment period. This typically resolves within weeks after the last session. Retrograde amnesia is loss of memories from before treatment. This can range from patchy gaps in the weeks surrounding treatment to, in rarer cases, loss of memories from months or even years prior.
For most people, anterograde memory bounces back relatively quickly. Retrograde memory loss is more variable. Some patients recover lost memories over time, while others experience permanent gaps. The risk is higher with bilateral placement, more frequent sessions, and standard (rather than ultrabrief) pulse widths. Confusion immediately after each session is common but usually clears within an hour.
Staying Well After ECT
One of the biggest challenges with ECT isn’t getting better. It’s staying better. Without follow-up treatment, the relapse rate is striking: up to 84% within six months. This is the single most important thing to understand about ECT. It is powerful at breaking a depressive episode, but it does not, on its own, prevent the next one.
The most effective strategy for staying well combines ongoing “maintenance” ECT sessions (spaced further apart, perhaps monthly or every few weeks) with medication. In a randomized trial comparing approaches over one year, 61% of patients relapsed on medication alone, compared with 32% who received both maintenance ECT and medication. Medication combinations also matter. One study found that a two-drug regimen reduced six-month relapse to 39%, compared with 60% on a single medication and 84% on placebo.
The bottom line is that ECT is best understood not as a one-time fix but as a tool that works in phases: an acute course to pull someone out of severe depression, followed by a sustained plan to keep them there.