BLOOMINGTON - About 10 percent of men and about 20 percent of women have diagnosable depression, meaning depression that is beyond a response to a loss or illness, said Dr. Scott Hamilton.

Psychotherapy (counseling) and antidepressant medicines are helpful to many people with mild to moderate depression, said Hamilton, a psychiatrist with Professional Associates of Illinois and medical director with the McLean County Center for Human Services.

Psychotherapy helps people who need to change how they think of things or how they interact with others. Antidepressant medicines increase activity of a brain chemical called serotonin (which modulates brain function and helps reduce anxiety and obsessive behavior), and affects dopamine (which helps attention, activity, motivation and pleasure sensation) and norepinephrine (which helps attention, abstract thinking, calculating and pain modulation).

People with severe depression also may be given electroconvulsive therapy (ECT), in which electrical stimulus is made to the brain, a seizure is induced and there is a massive release of neurotransmitters in the brain, Hamilton said. While some people experience a lessening of depression after this treatment, the benefit is temporary and there are risks, such as short-term memory loss, he said.

VNS (vagus nerve stimulation) therapy is a new treatment for people with treatment-resistant depression, meaning they haven't responded to at least four antidepressant drug treatments.

"VNS increases their chances," Hamilton said.

An electrical stimulus generator (about the size of a pocket watch) is implanted in the upper chest just below the skin and wires are run under the skin to the left vagus nerve in the neck.

The vagus nerve is the body's information superhighway, connecting the brain and many major organs, according to VNS therapy creator Cyberonics Inc. The nerve goes up to areas of the brain that release norepinephrine and serotonin and that regulate mood, motivation, sleep and appetite, Cyberonics said.

Every five minutes for 30 seconds, an electrical stimulation is sent from the generator to the vagus nerve, which sends it to the brain. The stimulation affects the production of neurotransmitters, which influence mood, motivation, sleep and appetite. The generator is adjusted from time to time to make sure the stimulus is at an appropriate intensity.

"It takes awhile for there to be a measurable benefit," Hamilton said. "There isn't a lot of difference in the first eight to 10 weeks but most people respond by a year."

The main side effect is a feeling of tightening of the vocal cord during stimulation because the vocal cord is near the vagus nerve. That's minor compared to side effects of some medicines, including weight gain, dry mouth, gastrointestinal problems, muscle twitches and sleepiness, Hamilton said.

The generator or its batteries need to be replaced every three to eight years.

Hamilton said most VNS patients will continue to take antidepressant medicines but may require less medicine. He hopes they will not need further ECT treatments.

Most insurance companies and Public Aid are covering the cost of VNS therapy in appropriate patients, Hamilton said.