At the age of 18, Rob Matte was a student, a competitive cyclist and an outgoing person with lots of friends. Then he fell into an emotional dark hole. For years Matte tried just about every treatment available for depression--antidepressant drugs, talk therapy and even 18 rounds of shock therapy. Nothing worked. All but two long-suffering friends had abandoned him. Relations with his family were strained. He had no interests and no job, and he spent most of his days in bed. He had began to think that the only way out was suicide.

Then in 2002, eight years after he was diagnosed with depression, Matte agreed to be a guinea pig for neurosurgeon Andres Lozano and Dr. Helen Mayberg at the Rotman Research Institute at Baycrest Centre and Toronto Western Hospital, who were testing a radical new treatment for depression called deep-brain stimulation. They implanted four electrodes deep into Matte's brain, ran wires down to his chest and hooked them up to a battery inserted under the skin. When they pressed a button, imparting a current to Matte's brain, it was as if a fog had cleared. "The operating room got brighter," he says. "It was like all the lights and colors got more vivid." Mood improvements soon followed. "I'm physically well," says Matte. "I'm feeling stronger. I'm able to do things." Matte has returned to his job as a laboratory technician.

For all the progress in drugs and talk therapy in the past two decades, one in five patients suffering from depression and obsessive-compulsive disorder--an estimated 50 million people in all--fail to respond to any of these treatments. Deep-brain stimulation is emerging as a potentially powerful alternative treatment. The idea behind DBS is that some patients suffering from mental illnesses show hyperactivity in some part of their brains. A small dose of electric current dampens neural activity, the theory goes, alleviating the problem as easily as turning on a light.

Doctors have had a long fascination with the notion of putting mental patients under the knife. Trephining, the 5,000-year-old practice of drilling big holes in the skull, was thought to release demons. The prefrontal lobotomy--which involved severing the nerve fibers that connected the frontal lobes with the thalamus, a region that processes sensory information--was widely performed on schizophrenics and paranoics and 1930s and 1940s, and in the 1950s was even used on homosexuals, unruly children and violent sociopaths. Doctors in the United States and Canada still practice psychosurgery on a few dozen patients a year--usually the most severe cases of obsessive-compulsive disorder and depression. Brain-imaging technology allows surgeons to pinpoint the exact location of hyperactivity in the brain and burn them with radiation. Although this procedure doesn't turn patients into zombies, as the lobotomy did, they carry the risk of stroke, infection and in some cases personality change. Deep-brain stimulation has one big advantage over radiation: it causes no permanent damage, and it is completely reversible.

DBS was first used in the 1960s to treat people with chronic pain, and in the 1990s doctors began using the technology to treat Parkinson's patients. In 1998, Dr. Bart Nuttin at the Catholic University of Leuven, Belgium, performed the first DBS surgery for patients with obsessive-compulsive disorder. A 39-year-old female patient who had suffered from extreme OCD for more than 20 years was relieved of anxiety and obsessive thinking as soon as the DBS was switched on. After two weeks, her parents reported that 90 percent of her compulsive behavior had ceased; on average, there was a 50 percent improvement in patient's symptoms after the procedure.

Although the use of DBS to treat depression is in the early stages, the results are promising. Lozano and Mayberg, who published their research earlier this month in the journal Neuron, treated six subjects who had failed all other forms of therapy. Jean Harris, 50, had suffered from depression for years. In one six-month stretch, she would bathe and change her clothes only before her weekly visits to the doctor. A few hours after the procedure, she went home and clipped her hedges. A year after the electrodes were first implanted, Harris, Matte and two other subjects who responded to the treatment are still free from the debilitating effects of their depression. Two subjects failed to respond to the treatment.

Despite these results, most psychologists remain hostile to the idea of psychosurgery. "It is quite damaging to the individual to say that the problem lies within their head," says Peter Kinderman, a psychologist at the University of Liverpool. Besides, DBS carries a small risk of infection. Rob Matte had to have the procedure done a second time after the first caused such a severe infection that doctors put him on an antibiotic drip for eight months. The procedure itself it no picnic either. "It's probably the most painful thing, physically, that I've had done to me," says Matte. "You have to be awake for the whole procedure. They give a local anesthetic, but they can't freeze your skull, like they freeze your skin." Another downside is that DBS requires a good jolt of current, which means the battery can run out in five months.

Because nobody really knows what causes depression, some neuroscientists argue that it's foolish not to keep an open mind about treatments--especially when it comes to the most severe cases. "These people are desperate," says Nuttin. "Some of them are suicidal. If you can operate on someone who will die of cancer, then nobody has problems with that. So if, from a psychiatric disorder, a patient's life is in danger, why not do an operation for that?" For people like Matte, who fall through the cracks, at least now there's an option.