Most people's mental image of ECT comes from films, and it is wrong. Here is what the clinical literature actually describes.
ECT is a medical procedure carried out under general anaesthetic. A carefully controlled electrical current is passed through the brain to produce a brief, generalised seizure. The person is asleep throughout and does not experience the seizure the way the films depict.
This review from Harvard Review of Psychiatry describes ECT as the most effective treatment available for several serious psychiatric conditions, including depression that has not responded to other treatments, bipolar depression, mania, catatonia, and schizophrenia that has not responded to clozapine.
The technique has changed enormously since the 1930s, with a great deal of work going into making it safer and reducing effects on memory and thinking. The review is clear that these issues have not been eliminated, and that understanding how ECT works is still an active research question.
Knowing what a procedure actually involves usually makes it less frightening than imagining it. If ECT has been raised for you or someone close to you, asking your treating team to walk you through the practical steps is a completely reasonable request — and a good place to start.