But now, CBS News Medical Correspondent Elizabeth Kaledin reports, there may be another option.
It's a tiny little device called the vagal nerve stimulator.
"It's very similar to a cardiac pacemaker in the sense that it will stimulate in a rhythmic fashion the left vagus nerve," says psychiatrist Dr. John Barry.
Doctors believe the left vagus nerve controls mood centers in the brain. When the device is installed, wires wrap around the nerve and deliver an electrical pulse, programmed by a computer. Psychiatrists like Barry believe the device has great potential.
And so does Tucker Davis. Before he was exposed to this experimental treatment, Davis knew the feeling of going under, and gasping for airnot because he's a scuba instructor, but because he has suffered from severe depression much of his life.
"There was no future to my life. I was just a burden on everybody and had no reason to be here," he recalls.
But today Davis sees many reasons, thanks to the vagal nerve stimulator.
After having the device surgically implanted in his chest wall, Davis felt better within about four months. The only side effect: it affects his speech. As the vargus nerve also affects the larnyx, Davis finds it makes his voice deeper.
The device has been used for years to treat epilepsy. But doctors discovered that epileptic patients were reporting vast improvements in mood, whether or not their epilepsy got better. So the idea was born to try it for depression.
Barry believes it would be a tremendous breakthrough, and Elizabeth Maynard Schaeffer thinks it could be a powerful weapon in her fight against severe depression.
Schaeffer is hoping to try the device since 30 drugs have failed her and she now relies on electric shock treatment every 3 to 5 months to control her depression. But electric shock often robs the brain of memories. And she is looking for anything new.
"It would be wonderful to have something there that worked consistently," says Schaeffer.
The vagus nerve stimulator is not for everyone. Nationwide trials are including people with chronic, untreatable depressionpeople like Schaeffer and Davis who, until now, had little hope for relief.