Associate Professor Ziad Nahas of the Medical University of South Carolina led the study that delivered electrical charges to parts of the brain's cortex - the anterior frontal and lateral prefrontal areas.
"We focused on these two regions because they are part of a larger brain network critical in regulating mood," said Nahas. "Both play complementary roles integrating emotional and cognitive experiences and offer a distinct opportunity for targeted antidepressant treatments."
He said such cortical stimulation has important advantages in the treatment of depression. "It is reversible, non-destructive and potentially safer than other forms of invasive brain stimulation since the stimulating paddles don't come in direct contact with the brain," he said.
The researchers implanted electrical leads in five patients with recurrent depression who were not responding to a variety of other treatments. The leads were connected to generators surgically implanted in each patient's upper chest. The devices delivered periodic electrical charges at intensities below the seizure threshold, and were inactive at night.
After seven months, the five patients had average improvements of 55 percent to 60 percent and three reported their depression had remitted, the researchers said.
The study appears in the early online edition of the journal Biological Psychiatry.