THE controversial psychiatric practice of using electric shock therapy to treat depression is undergoing an unlikely resurgence, with the number of treatments rising by more than 50 per cent in a decade.

Electroconvulsive therapy has emerged from the medical wilderness thanks to significant reductions in side effects, dramatic improvements in safety, and the belief by a growing number of psychiatrists that it is the most powerful treatment for chronic low mood.

Medicare data shows the number of government-funded treatments rose about 55 per cent from 12,480 in 1997-98 to 19,026 in 2007-08, costing the taxpayer more than $7 million.

"ECT is, without question, the most effective short-term antidepressant we have," says the world's top expert on ECT, Harold Sackeim, from Columbia University in New York.

Delivering the fourth Black Dog International Lecture in Sydney this week, Professor Sackeim said ECT could be considered for 20 to 40 per cent of patients suffering continuing suicidal or severe depression.

One in five people experience depression at some stage of their lives, according to beyondblue, the national depression organisation. But the first line of treatment, antidepressant medication such as Prozac and Zoloft, does not work for about 30 per cent of patients.

The Royal Australian and New Zealand College of Psychiatrists has endorsed ECT for people who have not responded to antidepressant medication, are psychotic, suicidal or catatonic. It says advances in equipment and methodology have produced less short- and long-term amnesia, and any memory loss is usually resolved in four to six weeks.

Associate Professor Colleen Loo, from the School of Psychiatry at the University of NSW, said the stigma surrounding ECT, due in part to horrific practices at Sydney's infamous Chelmsford Hospital and films such as One Flew Over The Cuckoo's Nest , where it was used as a tool of terror and behaviour control, still lingers in the public's mind.