THURSDAY, Oct. 14 (HealthDay News) -- A treatment for major depression that uses intense magnetic pulses to stimulate the brain, previously shown to reduce acute symptoms for brief periods, appears to work over the longer term when teamed with antidepressants, researchers report.

"We wanted to address the question of whether the benefit of TMS [transcranial magnetic stimulation] can be sustained over a reasonable time," said study leader Dr. Philip Janicak, a professor of psychiatry at Rush University Medical Center in Chicago. "Based on this trial, the answer is yes."

While the study is too small to be definitive, "it indicates that we can maintain the benefit of TMS over six months, and do it safely -- there were no further risks associated with the use of TMS in combination with antidepressant drugs," said Janicak.

The study was published in the October issue of Brain Stimulation.

Researchers randomly assigned 301 people diagnosed with major depression to either real or "sham" magnet therapy for six weeks. The sham treatment felt similar to the real one, but delivered very little of the pulse intensity of the real treatment.

The 142 people who received and responded to the real therapy then entered a 21-day transition phase. During this time, they were tapered off TMS and started on antidepressant medication, a standard treatment to prevent relapse.

Of those 142 people, 121 (85 percent) completed the transition phase without relapsing, and 99 agreed to enter a 24-week, follow-up study.

During this six-month period, only 10 of the 99 (10 percent) relapsed. Of 38 people whose symptoms worsened, requiring additional TMS sessions, 32 of them (84 percent) improved and avoided relapse. Altogether, 75 percent maintained full response to the treatment.

The study provides valuable information, said Tony Tang, an adjunct professor of psychology at Northwestern University. "We now know that with two safeguards in place -- one, that TMS responders are put on maintenance antidepressant medication, and two, they receive additional TMS treatments if their symptoms worsen -- TMS can work" for an extended period, he said.

Because depression tends to recur, it is important to consider any treatment's long-term performance, added Tang. "In that regard, the best treatment is high-quality CBT [cognitive behavioral therapy]. CBT works as well as maintenance antidepressant medications in preventing relapses, but without the side effects and costs of long-term medication." But if neither CBT nor antidepressants work, TMS may be an option, he said.

In TMS, an electromagnetic coil placed on the head delivers brief magnetic pulses through the scalp and into the part of the brain linked to depression, the left prefrontal cortex. The pulses, about as strong as those in a standard MRI scan, stimulate the nerve cells in that region. It's thought that this stimulation "resets" electrical activity in this region, thereby improving depression.

A study of 190 people with major depression published earlier this year, which also compared real and sham TMS, found that the real thing significantly improved major depression in those who hadn't been helped by antidepressants. In that study, after three weeks of treatment, 14 percent of people who received real magnet therapy recovered from their depression, compared to 5 percent of those who received the sham treatment.

In 2008, the U.S. Food and Drug Administration approved the first TMS device to treat depression in adults who weren't helped by at least one antidepressant. Treatments last about 40 minutes and are given five days a week for four to six weeks. Magnet therapy can cause mild side effects, including headaches and discomfort at the coil site.

Some 250 treatment centers around the country offer magnet therapy. People are either referred by their doctor or are evaluated by a center to determine their suitability for the treatment.

Since TMS isn't typically covered by health insurance, most people pay out of pocket. Standard treatments cost $7,000 to $12,000. However, some insurance companies will pay for the treatment after an internal review, and at least three insurance groups cover it on a policy-wide basis, said Janicak.

The study was funded by Neuronetics, Inc., which makes the TMS device used in the study.

More information

There's more on the treatment of depression at the U.S. National Institute of Mental Health.