The use of a treatment seen as a last resort for psychiatric patients has emerged among new details of an attack on two Upper East Side therapists that left one dead and the other injured.

Both the injured psychiatrist and the man charged in the attack, David Tarloff, had ties to electroconvulsive therapy, or ECT, colloquially known as shock therapy, in which doctors induce a seizure through electrical shocks administered to the temples. It is used to treat severely depressed or manic individuals for whom other treatments have failed.

Mr. Tarloff, who has had a long history of mental illness, had received ECT, his family told the New York Times. The injured psychiatrist, Dr. Kent Shinbach, also had an interest in the therapy, and in 1984 he co-wrote a paper studying the effect of ECT on patients who used the drug phencyclidine, or PCP. It is not clear whether Dr. Shinbach played any role in Mr. Tarloff’s shock therapy.

Psychiatrists said ECT is often a last resort for severely depressed patients. It is a legal, medically accepted, and widely available treatment used by an estimated 100,000 patients nationwide each year. Despite its negative portrayal in popular culture, the American Psychiatric Association issued a position statement last year that described ECT as a “safe and effective” treatment for certain disorders.

“To put it simply, ECT is the most effective and rapid-acting treatment we have for severe depression,” the chief of the Brain Stimulation and Modulation Division at Columbia University and the director of the Brain Behavior Clinic at the New York State Psychiatric Institute, Dr. Sarah Lisanby, said.

“Normally, ECT would be reserved for people who have failed conservative treatment,” the editor of the Journal of ECT and the chairman of psychiatry at Wake Forest University, Dr. Vaughn McCall, said.

Still, the therapy has a reputation for being barbaric and dangerous, thanks largely to movies such as “One Flew Over the Cuckoo’s Nest,” in which the actor Jack Nicholson portrayed a psychiatric patient who received ECT.

ECT was most popular in the 1950s and 1960s, but it declined with pharmaceutical development during the 1970s and 1980s. It experienced a slight comeback during the 1990s when technological advancements improved safety and reduced side effects, such as memory loss.

Some consumer groups, however, said ECT can cause broken bones or brain damage.

“It’s inherently brain damaging. To have any kind of electroshock, you have to have a convulsion,” said David Oaks, the executive director of MindFreedom International, a group that opposes forcibly administering ECT to psychiatric patients.

Proponents of ECT defend the therapy as safe and say patients are sedated during the procedure. Technological advancements have allowed doctors to administer ECT with more precision and smaller doses of electricity, they say.

To some, ECT is sometimes seen as the only thing that works. “Over half the patients I’ve treated have tried to kill themselves in recent weeks,” a professor of psychiatry and radiology at Columbia University, Dr. Harold Sackeim, said.