Up to 40 percent of people with depression do not respond to antidepressant medication. For these patients, hope may come in the form of transcranial magnetic stimulation, or TMS, a technique that activates neurons by sending pulses of magnetic energy into the brain.

Although researchers have been studying the effects of TMS on depression for more than 10 years, it has been largely viewed as an experimental procedure because of concerns about safety issues, such as seizures. Now psychiatrists at the University of Pennsylvania report successful results from the largest-ever trial of TMS, countering many critics’ doubts. The team tested about 300 patients with major depression who had failed to respond to medication and found that those who received about 40 minutes of TMS daily for four weeks experienced significant symptomatic improvement. No major side effects were reported, although the technique is not recommended for anyone with a history of seizures.

TMS delivers its neuron-activating magnetic field via small metallic coils attached to the scalp, which investigators can position to target specific brain areas. In this study, the team
targeted a region of the prefrontal cortex previously shown to be less active in depressed subjects. Because TMS is both noninvasive and precise in aim, the technique readily lends itself to unusual research, from triggering ordinary people’s inner mathematical savant to studying the root of religious experience (in its incarnation as the “God helmet” [see “Searching for God in the Brain,” by David Biello; Scientific American Mind, October/November 2007]).

Although TMS is already available to patients in Australia and Canada, stricter regulations mean it could be several months to years before patients in the U.S. have access to the therapy, says John O’Reardon, lead author of the new study. He and other experts believe that eventually TMS will also help patients with schizophrenia, bipolar disorder and Tourette’s syndrome.