After 22 years of failed treatments, including rehabilitation, psychotherapy and an array of psychiatric medications, a middle-aged Dutch man decided to take an extraordinary step to fight his heroin addiction. He underwent an experimental brain surgery called deep brain stimulation (DBS). At the University of Amsterdam, researchers bored small holes in his skull and guided two long, thin probes deep into his head. The ends of the probes were lined with small electrodes, which were positioned in his nucleus accumbens, a brain area near the base of the skull that is associated with addiction.
The scientists ran the connecting wires under his scalp, behind his ear and down to a battery pack sewn under the skin of his chest. Once turned on, the electrodes began delivering constant electrical pulses, much like a pacemaker, with the goal of altering the brain circuits thought to be causing his drug cravings. At first the stimulation intensified his desire for heroin, and he almost doubled his drug intake. But after the researchers adjusted the pulses, the cravings diminished, and he drastically cut down his heroin use.
Neurosurgeries are now being pursued for a variety of mental illnesses. Initially developed in the 1980s to treat movement disorders, including Parkinson's disease, DBS is today used to treat depression, dementia, obsessive-compulsive disorder, substance abuse and even obesity. Despite several success stories, many of these new ventures have attracted critics, and some skeptics have even called for an outright halt to this research.
One major misgiving is that recent applications may be outpacing their scientific support. Unlike the cautious early investigations of DBS for depression, carried out by neurologist Helen Mayberg of Emory University and her colleagues, the latest trials have been conducted less meticulously. Although these procedures are often considered low risk, as Mayberg once pointed out, “there is no such thing as minor brain surgery.”
Lobotomies are perhaps the most infamous example of “psychosurgery.” This procedure, which involved cutting the connections between different parts of the brain, has always been controversial. Only in the 1970s did concerns about its misuse drive these surgeries to extinction in the U.S. Similar techniques, such as freezing or cutting certain brain areas, persisted in China and Russia at least through the early 2000s.
DBS seems more palatable than these gruesome-sounding methods and rightly so. It is more precise: electrodes are guided to within a millimeter of their target to stimulate a specific brain area. DBS is also considered reversible because the electrical stimulation can easily be turned off. The risks of this procedure—including brain hemorrhage, infection or even death—are dire but uncommon.
The first brain area targeted for depression was chosen after years of painstaking neuroimaging research, but recent advancement in DBS has come as much from luck as from planning. Consider, for example, the serendipitous manner in which it was discovered that DBS might treat addiction. In 2006 psychiatrist Jens Kuhn of the University of Cologne in Germany and his colleagues tried DBS on a patient with a particularly bad case of panic disorder. The man's anxiety did not change, but he reduced his alcohol intake considerably without intending to do so. The researchers realized that in other experiments, stimulation to the same brain region, the nucleus accumbens, had also led to unintended, spontaneous reductions in drinking and smoking. Soon researchers were testing DBS on cocaine- and morphine-dependent rats, and in the past few years scattered reports of DBS for people with drug and alcohol problems have also emerged.
Other unintended side effects have also spurred new uses of this poorly understood technology. The case of obesity is instructive here. Despite not being a traditional mental disorder, obesity has become an enticing target for DBS. In 2013 neurosurgeon Donald Whiting of the West Penn Allegheny Health System and his colleagues reported that by stimulating the lateral hypothalamic area (the “feeding center” of the brain) of three people with intractable obesity, they could reduce their patients' urge to eat. Two of the three participants lost a significant amount of weight during the two-year study.