For chronically depressed adults who find no relief with drugs or psychotherapy, an implanted pacemaker-like device that sends electrical pulses to the brain - so called vagus nerve stimulation - may provide long-term benefits, according to two reports this week at the American Psychiatric Association annual meeting in Toronto.

“With other treatment methods, if you get a response among treatment-resistant depression patients, it is rare that they are able to hold on to that response,” presenter Dr. Stephen K. Brannan told Reuters Health. Even with shock therapy, within 6 months the majority of patients have relapsed, he said.

“What is really interesting in our study was that the onset of effect was slow, but once they get it, the benefit seems to last a long time,” the researcher continued. “This is hugely different from anything I’ve seen in this field before, because these patients usually have the illness for the rest of their lives.”

It is estimated that 10 percent to 20 percent of patients with major depression have treatment-resistant depression. According to the FDA, only patients who have failed four other types of treatment can be considered candidates for vagus nerve stimulation.

Brannan at Cyberonics Inc. in Houston, Texas, and colleagues conducted a pilot study of vagus nerve stimulation among 59 patients with treatment-resistant depression.

They found that 72 percent of patients who responded early (within the first 3 months) maintained their response at 12 months and 61 percent at 24 months. Among late responders, defined as response by 12 months, 79 percent remained stable at 24 months.

In a second pivotal trial that included 205 patients, 15 percent had an early response, and 31 percent a late response. Maintenance of response was similar to that of patients in the pilot study.

“Even among those who had only a 40 percent or 30 percent response, that may be quite meaningful,” Brannan commented. “That level of response may mean that the patients are no longer suicidal, no longer require hospitalization, and they may even return to work.”

The second presenter, Dr. William J. Burke from the University of Nebraska in Omaha, reported that treatment-resistant patients undergoing vagus nerve stimulation experienced a steady decline in suicidality over 24 months of treatment. His study cohort was the same 205 patients evaluated in the pivotal study by Brannan’s group.

“We looked at the numbers who tried to attempt suicide, who reported suicidal ideas, and who were hospitalized because of worsening depression,” Burke said. “All three measures declined throughout the 2-year study. During the last 6 months, there were no suicide attempts, and the number reporting suicidal ideas was very low.”

He noted that the number of patients who were suicidal or hospitalized peaked during the first and second quarter, then “gradually and substantially decreased over time.”

“It almost perfectly mimics what you see in terms of response to vagus nerve stimulation,” he added. Without it, “the risk of suicide among patients with treatment-resistant depression is fairly constant over the lifespan.”

In a second arm of the pivotal study, Dr. David L. Dunner from the University of Washington in Seattle, and colleagues followed patients with treatment-resistant depression who were treated over 2 years with “treatment as usual,” including medications, psychotherapy, and shock therapy.

Only 13 of 124 patients could be classified as responders at 12 months, five of whom maintained their response at 24 months.

Based on all three studies, Burke considers vagus nerve stimulation to be a cost-effective option for treatment-resistant depression. The cost of vagus nerve stimulation is roughly what it costs to have a single course of shock therapy in a hospital, “so there is no doubt that (it) is cost-effective for this type of depression that does not respond to anything else.”