High-speed magnetic resonance imaging scans produce effects in rats similar to the use of antidepressants, confirming observations made in human patients, U.S. researchers reported on Thursday.

The finding suggests that magnetic fields can affect brain biology, the team at McLean Hospital and Harvard Medical School reported.

“We found that when we administered the magnetic stimulation to the rats, we saw an antidepressant-like effect, the same effect as seen after administration of standard antidepressant drugs,” said William Carlezon, director of McLean’s Behavioral Genetics Laboratory.

Writing in the journal Biological Psychiatry, Carlezon and colleagues said they tested the rats after another team at the hospital reported a new type of magnetic resonance imaging, called echo planar magnetic resonance spectroscopic imaging (EP-MRSI), had improved the mood of people in the depressed phase of bipolar disorder.

The new study was designed “to see if we could demonstrate in an animal model what the clinicians thought they were seeing in humans,” Carlezon said.

When repeatedly stressed, rats develop helpless behavior, which may be their version of despair, the researchers said. But in the experiment, the rats that had been exposed to EP-MRSI showed less helplessness during the stress tests.

“They behaved as if they had received an antidepressant,” said Dr. Bruce Cohen, psychiatrist in chief at McLean.

“It’s a non-drug way to change the firing of nerve cells,” Cohen said. “That’s why the implications of this work have the potential to be so profound.”

While this may offer a new way to treat Depression, it also suggests that at least some forms of MRI are more invasive than previously thought, the researchers said.

“Renewed caution is warranted when high-speed MRI is used to diagnose or study disorders involving the brain,” the researchers wrote.

“People assume when they are getting an MRI that nothing is happening, that you are simply getting a picture of the brain. But in actuality the body is being exposed to magnetic and electrical fields,” Carlezon said.

“They may cause other effects we don’t understand yet,” he added.