Luc Mallet and colleagues at the National Institute for Health and Medical Research, headquartered in Paris, conducted a clinical trial of the technique in patients for whom other treatments have not helped severe obsessive compulsive disorder -- a psychiatric disorder marked by hours-long anxiety-reducing rituals such as hand washing.

Patients divided among 10 university hospitals received surgical implantation of an electrode in a precisely mapped area of the brain that over the course of 10 months was activated and then deactivated in a randomly determined order. Eight patients underwent a period of active stimulation followed by a period of "placebo" stimulation while eight others received "placebo" stimulation followed by real stimulation.

"This was a double blind test -- neither the patients nor the doctors knew the periods of stimulation," Mallet said in a statement.

The study, published in the New England Journal of Medicine, found that at the end of three months of active stimulation, seven patients out of 10 lost more than one-quarter of their symptoms and six out of 10 reached satisfactory overall functioning. Twelve percent reached satisfactory overall functioning with placebo stimulation.