Deep electrical stimulation of the brain may help alleviate severe, chronic depression in patients who don't respond to other treatments, researchers in Ontario have found.

To test an experimental surgery, doctors placed devices in both sides of the brain of six people. They had all been treated for depression with drugs and talk therapy, and in some cases, electroshock therapy.

None of the conventional treatments worked for them.

Scientists stimulate a sadness centre in the brain's frontal lobe.

The experimental treatment consists of a pacemaker implanted under the collarbone, as well as electrodes in the brain.

When neurosurgeons applied an electrical stimulation to the electrodes, four of the six patients showed remarkable improvement in mood and sleep, the study's authors reported in this week's issue of the journal Neuron.

The researchers hypothesized that by targeting an area of the brain's sadness centre, they could treat depression. The technique has been used since the late 1990's to treat tremors in patients with Parkinson's disease.

Dr. Andres Lozano.

The sadness centre, called Cg25, is thought to play a critical role in sadness and mood. People with depression may have too much activity in the part of the brain, scientists speculate.

"We thought that one strategy might be to go in and try to turn down the activity in these areas and to see whether that would have any benefit," said Dr. Andres Lozano, a neurosurgeon at Toronto Western Hospital.

The improvements were immediate and lasted beyond the six months of the trial. One patient, Jeanne Harris, said three months after the device was activated, she went out shopping, an activity she hadn't done in years.

Another patient said he's thinking of returning to work. "It's like you've suddenly awakened from a long sleep," said Rob Matte. "Wow, there's things I want to do."

The results of the experiment need to be repeated in more patients to make sure the effect wasn't a fluke. Other questions still need answers.

"Who will it be good for, who will it not?" asked Dr. Claire O'Donovan, a psychiatrist and director of the Mood Disorders Clinic at the QEII Health Sciences Centre in Halifax. "How long will it take before it has any clinical impact?"

Since surgery always carries risks, psychiatrists say deep brain stimulation will likely only be an option for the most serious cases of depression.