Patients who engage in cognitive or "talk" therapy to recover from depression show brain changes that differ from what occurs with drug therapy, new research finds.

The study shows for the first time with imaging evidence that the depressed brain responds differently to different treatments -- and the results may help doctors understand why one treatment works for one patient but not another, says study author Dr. Helen Mayberg. Her report appears in the January issue of the Archives of General Psychiatry.

Mayberg, an associate scientist at the University of Toronto's Rotman Research Institute at Baycrest Centre for Geriatric Care, and her team looked at 14 adults with clinical depression who received 15 to 20 sessions of outpatient talk therapy without any drug treatments. They gave the patients brain scans before and after therapy using positron emission tomography (PET), which pinpoints the areas where the most changes in brain metabolism occur. They compared the results to typical changes that have been found with drug therapy

They found both therapies affected many of the same regions in the brain, but in different ways.

"One [treatment] isn't better than the other," says Mayberg, who is also a professor of psychiatry and neurology at Emory University School of Medicine in Atlanta. "Different treatments work on the brain in different ways."

In drug therapy, the brain chemistry is altered in the bottom regions of the brain, such as the limbic region, areas that drive basic emotional behaviors, according to Mayberg. It's considered a "bottom-up" approach.

Talk therapy is termed a "top-down" approach because it focuses on changes in the cortical -- or top -- areas of the brain, regions associated with thinking functions, to change abnormal mood states.

With drug therapy, experts know that blood flow decreases in the bottom regions and increases in the top areas. But with talk therapy, blood flow increased in the bottom regions and decreased in the top regions.

Mayberg says the reverse pattern can be explained this way: As talk therapy patients learn to shut off the thinking patterns that lead them to dwell on negativity, activity in areas of the cortical or top regions decrease as well.

Dr. Aaron Beck, one of the originators of cognitive therapy and a professor of psychiatry at the University of Pennsylvania in Philadelphia, praises the new study. "It demonstrates that cognitive therapy does have a serious impact insofar as there are brain changes," he says.

"Clinically, we have documented the changes in depression [with talk therapy]," he says. Now, he adds, the study provides the subjective evidence that there are neurophysiological changes.

The findings, he adds, are consistent with the top-down theory of how cognitive therapy works. "You do get a kind of confluence between the two approaches in terms of the brain changes," he adds.

The findings may help doctors better decide how to treat depression, says Mayberg, using a combination of approaches. "The areas that cognitive therapy work in are areas that drugs don't touch," she says.