To start, we should say that ECT has a very bad rap from movies, such as "One Flew Over the Cuckoo's Nest", where it's portrayed as being a fairly abusive form of treatment. But, in reality, today it is still practiced in safe hospital settings where there is anesthesia present, and we use muscle relaxants so that people do not have the violent types of seizures that are portrayed in the films.
So, the process of electroconvulsive therapy is that an anesthetist puts you to sleep, there's an electrode applied to the scalp, and a seizure lasts very briefly, and is usually for a couple times or three times a week, for a few weeks, and then maybe maintained once a month.
Now, in schizophrenia, there's actually very limited evidence that it's effective. It's probably not more effective than medications for schizophrenia. And so, we usually use for people who have not benefited from multiple, multiple medication trials, and it's felt that this a treatment of last resort that might be helpful.
In contrast, ECT is actually really effective for depression. It's actually more effective than medications for depression, and it's actually safer than medications for people who are pregnant or who are very elderly or debilitated. But, because there is a risk of memory loss with ECT, we also are very sparing with our use of it.
The factors in schizophrenia that might make it more likely to respond to ECT include something where the onset is really rapid, where there are a lot of positive symptoms that might be more likely to respond. And yet, still, we usually focus on medication treatments for schizophrenia.