Every year, clinical depression afflicts more than 18 million Americans, many of whom don’t respond to conventional antidepressants like Prozac and Zoloft. But a promising new type of therapy is gaining wider use. The technique, called “transcranial magnetic stimulation,” uses pulses of magnetic energy to induce electric currents in specific brain regions. While no one knows exactly why it works, researchers say the treatment can alleviate depression.
Magnetic brain stimulation has been used experimentally for years. Mark George, a neurologist and psychiatrist at the Medical University of South Carolina in Charleston, SC, says that in a number of limited trials, the technique helped severely depressed patients-though modestly and for short periods. These early results have led to government approvals in Israel and Canada. But magnetic therapies have only recently entered large-scale human testing in the United States. A new study, launched in early 2004 and involving hundreds of patients at numerous centers, “should be pivotal” in gaining the U.S. Food and Drug Administration’s approval for the therapy in one to two years, says George. “It would be surprising if the therapy didn’t prove effective,” he adds.
A doctor typically holds a powerful magnet over the frontal regions of the patient’s skull and delivers magnetic pulses for a few minutes a day, over the course of a few weeks. The treatment alters the biochemistry and firing patterns of neurons in the cortex, the part of the brain nearest the surface. Preliminary research indicates that the treatment affects gene activity, levels of neurotransmitters like serotonin and dopamine, and the formation of proteins important for cellular signaling-any of which could play a role in alleviating depression. What’s more, magnetic stimulation seems to affect several interconnected brain regions, starting in the cortex and moving to the deep brain, where new cell growth may be important in regulating moods.
One problem: doctors can’t be sure they are stimulating the same brain regions from patient to patient, or from session to session. A system developed by Malvern, PA-based Neuronetics is part of the new trials; it uses state-of-the-art magnetic materials to generate pulses efficiently and a positioning system that supports the magnet and records its location in three dimensions. That means more repeatable treatments and clearer study results, says Bruce Shook, Neuronetics’ president.
Researchers are beginning to understand how the therapies affect patients. Columbia University psychiatrist Sarah Lisanby is investigating a type of magnetic therapy in which seizures are induced under anesthesia. She is comparing its effects to those of electroconvulsive therapy, in which electrodes on the head provide electrical stimulation. In addition to noting effects on brain cells, she has found that magnetic seizure therapy produces fewer side effects, such as memory loss, than electroconvulsive therapy. “Activating these pathways in real time, we’re learning a lot about the brain circuits involved,” says Lisanby. And that allows doctors to hone the therapy by adjusting location, intensity, and pulse frequency.
One of the chief remaining questions is whether the positive effects of brain stimulation can be sustained. “It will take a few years to know how effective it is in patients” over the long term, says Ren Hen, a Columbia neurobiologist. But meantime, magnetic stimulation is attracting much attention from those trying to fight depression.
Leaders in Magnetic Brain-Stimulation Therapies
|Mark George, Medical University of South Carolina (Charleston, SC)||Imaging the brain and improving techniques for treating depression|
|Leon Grunhaus, Sheba Medical Center (Tel Hashomer, Israel)||Conducting clinical trials of depression treatments|
|Sarah Lisanby, Columbia University (New York, NY)||Conducting clinical trials with magnetic seizure therapy |
and studying biochemical mechanisms in the brain
|Bruce Shook and Mark Demitrack, Neuronetics (Malvern, PA)||Developing more efficient and reliable hardware|