They say it must not repeat the mistakes made during the era of lobotomy surgeries between 1939 and 1951, when thousands of patients were treated with little or no proof that lobotomies worked and with little or no follow up.
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Adds Dr. Thomas Schlaepfer, vice chairman of the department of psychiatry of the University of Bonn, Germany, "I [have] reviewed studies for obesity, anorexia, shyness, addiction, the most crazy indications you can think about. Everyone wants to get in the game early. . . . If things go haywire it might kill the whole field."
For one thing, deep brain stimulation is brain surgery. There can be complications -- such as bleeding, stroke, coma, death and infection.
Other risks may depend on where the electrodes are placed in the brain. After deep brain stimulation for Parkinson's disease, for example, patients may have problems with swallowing, obsessive compulsive disorder, gambling and dementia, and there may be an increased suicide rate.
It is unclear, Mayberg says, whether these effects are related to the stimulation or merely reflect the progression of the disorder.
Mayberg says that, over five years, no side effects have been observed in patients treated for depression with deep brain stimulation in a part of the brain called area 25. Perhaps, she speculates, the area where deep brain stimulation is done in Parkinson's disease patients has more signal traffic between nerve cells than does area 25.
But Schlaepfer suggests that side effects aren't yet observed in patients treated for depression because the number of treated patients is still too small.
Schlaepfer says the two large clinical trials being conducted on deep brain stimulation for depression may be premature.
In a trial, he says, one needs to keep the area of stimulation constant in every patient. But only about 50 depressed patients so far have been treated with deep brain stimulation, and "it's just not enough to make an informed decision on what the right target [in the brain] is," he says. "This research is mainly driven by industry and not by public funding, [and] it's going a little bit too fast for my taste."
Dr. Joseph Fins, chief of the division of medical ethics and a professor at Weill Cornell Medical College in New York, thinks the Food and Drug Administration may have acted too soon in granting a "humanitarian device exemption" to deep brain stimulation for severe obsessive-compulsive disorder. This will allow patients to receive the therapy outside of clinical trials, he says -- and there won't be a systematic collection of data, making effectiveness that much harder to establish.
In addition, small experiments on just a few patients don't always get published, says Dr. Andres Lozano, professor of neurosurgery at the University of Toronto and president of the World Society for Stereotactic and Functional Neurosurgery. "Sometimes there are only two patients," Lozano says. "Then, unless [the findings] are published, you don't necessarily hear about them."
Some have suggested guidelines for patient selection. And in a February editorial in the journal Biological Psychiatry, Dr. Wayne Goodman of the National Institute of Mental Health and NIMH director Dr. Thomas Insel called for a registry of all deep brain stimulation studies to make sure that all cases get follow-up to learn what does and doesn't work.
Deep brain stimulation research also raises ethical questions, such as how to make sure patients who may have diminished capacity to consent understand the risks and benefits of participating in the trials. In 2007, researchers met to discuss such issues. Recommendations will be published in an upcoming paper.
Some issues with deep brain stimulation have to do with what happens when the procedure succeeds. One of his depression patients, Schlaepfer says, lost his girlfriend because she couldn't deal with his newly found independence.
"She didn't like [that] he was not a poor guy anymore and started to be more normal," Schlaepfer says, "which was something [we] never anticipated."