Happiness is a Warm Electrode

Deep-brain stimulation takes another approach, targeting the electrical signals that facilitate the chemical communication. The exact mechanism affected is still undetermined, but Rezai suspects that DBS works on axons, the central conduits of each nerve cell. These protein-sheathed fibers act like miniature telecommunications cables, passing messages from one end of a cell to the other. Rezai thinks the added voltage may be increasing bandwidth in the axons, possibly allowing them to carry more information-and more of the right information. In the long run, he hopes, identifying damaged axons could help scientists develop new methods of diagnosing and treating depression.

The New Lobotomy?

But first Rezai must convince his colleagues that attacking depression with electrical current is a good idea. Patients like Hire, who don't respond to drugs, therapy or ECT, reveal how little modern science really understands about depression, which is one reason why DBS tends to raise thorny scientific and ethical questions. Most Parkinson's patients are in their 60s or older, but victims of depression might only be in their 20s. Will it be safe, wonders psychiatrist Neal Swerdlow of the University of California at San Diego, for them to have the hardware implanted for six or seven decades?

Then there's the fundamental problem of delivering happiness on demand. Hire's psychiatrist uses a handheld device to tune the voltage and frequency of the stimulators implanted in her chest. Although some patients might wish to manipulate the device themselves, Malone says self-control is unlikely. There's a risk of cranking the volts too high, potentially causing brain damage. "This is not cosmetic neurology," he says. "This is about treating a fatal illness." Yet the trial-and-error process of banishing depression is still as much art as it is science.