Drugs are the most common psychiatric treatment for depression. But about 40 percent of people fail to respond to this first-line of antidepressants. What to do? The answer to date has often been more and different drugs. 

But transcranial magnetic stimulation (TMS), a technique that can revive activity in neurons in the brain's prefrontal cortex using an electromagnet, has been receiving more attention as a possible treatment for these stubborn cases of depression. In 2008, the FDA approved TMS for this purpose. Data since that point has been promising, but questions remain: How does it compare to antidepressant drugs? Is it cost-effective?