After using electroconvulsive therapy for more than 70 years to treat severe depression, doctors say they now have discovered how it works.
Shock therapy, in use since 1937, appears to tamp down an overactive connection between two parts of the brain involved in emotional processing, thinking and concentration, according to a study released today by the Proceedings of the National Academy of Sciences.
The procedure mimics a seizure, sending a brief electric current to the brain. ECT has the strongest supporting data among treatments for patients whose depression doesn’t respond to medication, according to the American Psychiatric Association. About 10 to 20 percent of depressed patients receive shock therapy, said Paul Holtzheimer, an associate professor of psychiatry and surgery at Dartmouth Medical School.
“This gives us a much more powerful view of the brain,” Holtzheimer, who wasn’t involved in the study, said today in a telephone interview. “If this study holds up, it tells us this is a network problem.”
In the study, nine patients scheduled to undergo shock therapy had their brains scanned using functional MRI before and after treatment. This type of imaging detects blood flow to specific areas of the brain. Then the researchers analyzed the brain’s connectivity using a new mathematical model.
The finding suggests that this overactive connection is important, without saying why. A previous study, published in the journal PLoS had similar results, showing that depressed patients had more hyperactive connections compared with normal control subjects.
Understanding the connectivity is like understanding shipping routes. Counting the number of trucks in and out of Chicago gives a person a sense of what the shipping routes may be. However, when data such as the number of ships coming into San Francisco is known, and that is correlated with Chicago’s trucks, it gives a better understanding of how the routes work. This study begins to map Chicago and San Francisco for the brain’s connections, Holtzheimer said.
The decrease in connectivity didn’t directly correlate with a drop in depression, so it may be the case that something else is at play, Holtzheimer said. However, the region should be investigated, he said.
“It’s a huge opportunity in that it gives us a new tool in what to look for,” said Christian Schwarzbauer, a study author and neuroscientist at the University of Aberdeen in the U.K.
More study may lead to therapies that don’t have the side effects of ECT, he said. Confusion, memory loss and physical pain such as muscle spasms are among the side effects of shock therapy.
Also, a better understanding of how the brain region is affected in depression may enable doctors to better target patients who will benefit from treatment, Schwarzbauer said.
Two closely held companies sell devices for ECT, Somatics LLC of Lake Bluff, Illinois, and Mecta Corp. of Lake Oswego, Oregon. A typical course of therapy involves treatments three times a week for as many as four weeks, according to the National Institute of Mental Health.
One of the areas where the connections were lessened by shock therapy was the left dorsolateral prefrontal cortical region, which was previously known to be involved in depression. The area also plays a role in thought and decision-making. It’s located near the front of the brain, on the left side.
It may be that the brain’s hyperactivity in that region makes it less efficient in other areas, provoking the symptoms of lethargy and low mood that are frequently seen in depression, Schwarzbauer said.
“This is the start of a longer process,” he said. “This is a very novel finding.”