Catatonia. There is an excellent review on the effectiveness of ECT in the treatment of catatonic schizophrenia as well as episodes of catatonia here:http://www.Hta.Ac.Uk/fullmono/mon909.Pdf.
I've not found. Detailed statistics that would respond to a quantifiable query on the effectivenessof ECT for this condition have eluded my efforts. That said, ECT is the 1st or 2nd treatment of choice for this fairly rare condition. Even that is argued to be from 8% - 38% of psychiatric patients. Ect is used by professionals who believe in it and does seem to help people who've not had relief before. Best!
ECT? Why all the ECT questions? Nobody uses ECT as primary tx. Most likely used in a pregnant woman who is so depressed she is suicidal and mother and child are at risk of death.
Very effective. When properly diagnosed, and selected appropriately, ECT is an extremely effective and safe treatment option for catatonic schizophrenia.